I've created a spreadsheet containing the list of all the large ships so you can compare them.
It also contains a small list of where to find blueprints, skills book and equipment (let me know if you find more, since for now it contains only a small portion of them).

Inside this spreadsheet you can also find the basic for the Bermuda Maze dungeon (in order to buy/sell faster).

Here it is the link:
https://docs.google.com/spreadsheets/d/1XJ5laaka7fxcP7Qd2L32QZQYvZArjiTLVpHgz06gIBI

All ships can be modified to improve sailors, cargo, or the number of cannons.

When you modify a ship you need first to determine a role for it. There are 3 main roles:

• Melee: rush forward towards an enemy ship to stop the cannons and kill the sailors in melee combat. The damage of this ship is completely based on the number of sailors and the bosun leading them.
  
  
• Mid-Range: this ships has to stay further away than a melee ship, but still close enough for the mortars to take out sailors. This kind of ship also have the function of tanking damage and cover the melee ships. The damage of this ships should be focused on anti-personnel weapons (mortars), and they should also have enough sailors to take damage from enemy mortars without losing all sailors.
  
  
• Long Range: this ships are your top DPS, they can even sacrifice sailors in order to have as many cannons as you can.

Personally I use 4 melee, 2 mid-range and 2 long range, but you can easily make a 4 mid-range and 4 long range and it will work fine anyway.


Melee:
Melee ships are pretty easy to modify. Just increase the number of sailors as much as you can with forecastle, sterncastle, and by reducing the cabin for sailors quarters.

To reinforce the hull, you need speed then armor.

The melee ships in game are limited so you don't have much of a choice...

Best Ships:
1. Dreadnought-class Galleas
2. Arabian Giant Dhow
3. Galleas

To pick a figurehead, you need one that increases sailor health, damage and lethality.

Best Figureheads:
1. Eric Statue
2. Leviathan Statue
3. Nurse Statue
4. The Godess Statue

Captain Abilities:
Make sure you have 1 Quick Repair, 1-2 Rapid Treatment (in total not on the melee ships), and 1-2 melee specific abilities of your choice:
1. Raise Morale: increase the melee damage by 30% for a short time.
2. Conflagration: a continuous fire that burns enemy sailors fast while the ship is in combat.
3. Cast-and-Reel: a hook that pull a ship in melee range and kills a LOT of sailors (like 60% of them).

Crew:
Make sure to have a bosun with Health/Defense Boost + Suppression + Attack Boost (or Raiding).

Cannons:
For melee ships you can choose to use smoke cannons to block the enemy damage until they reach the target. Alternatively you can use small mortars to kill some sailor before they reach the target, but since we're speaking of a 4 cannon set the damage will be REALLY small.


Mid-Range:
Mid-range ships needs some balance, so first you need to pick a ship with a large base number of sailors and good armor. Now you need to sensibly increase the cannons count in order to mount 4 mortars and 1-2 smoke cannons. In total you need a number between 132 and 168 cannons max.
To increase the cannons, first calculate that a forecastle and sterncastle always increase the cannons by 10 each (the giant version), while the cabin modification increase by 10% (of the base count), exaple: a ship like the soleil with a 162 base cannons will increase by 16 the cannons count by modifying the cabin.
To increase cannons try to reduce the sailors first (compensate with the forecastle and sterncastle first if you can), then use some cargo space. DO NOT consume all cargo or all sailors with the 5 modifications or you'll either end up without supplies or with too few sailors to resist mortars (which is VERY important for this role).

To reinforce the hull you need armor then durability then speed (speed is nice but not critical).

To pick the best ship for the job, choose a ranged ship with high sailor count and high armor.

Best Ships:
1. Santa Catalina Heavy Armored Ship
2. Soleil Royal Naval Warship
3. Santa Maria Ocean Liner
4. Ragazzoni Sailboat

To pick a figurehead, you need one that increases durability and sailor health.

Best Figureheads:
1. Leviathan Statue
2. The Saint Statue

Captain Abilities:
You can use this ships to hold the Rapid Treatment, or you can use them more aggressively with Quick Reload to wipe out the sailors of enemy ships.

Crew:
Make sure to have a navigator with Quick Reload and Hit Rate. Speed and precision is more important in this case.

Cannons:
As said before, we need to mount 4 mortars (as big as possible, even 28), and with the remaining slots we mount 1-2 smoke cannons (as big as possible) to fill the remaining slot.
The mortars will wipe out the enemy sailors, while the smoke cannons will blind them reducing their damage.


Long Range:
Long range ships are pretty simple to modify. Just increase the cannons count to 196 (7 slots x 28 is the max you can get), and sacrifice sailors first then cargo. DO NOT sacrifice too much cargo or you'll end up without supplies.

To reinforce the hull you need durability then armor, speed is not really necessary since they won't have to move much.

To pick the best ship, choose the ship with high hit points and high base cannon count.

Best Ships:
1. Victory Naval Warship
2. Zheng He Treasure Ship
3. Holy Trinity Battleship
4. Triple-decker Galleon
5. San Juan Clipper
6. East India Large Oceanic Battleship

To pick a figurehead, you need one that increases firepower and durability.

Best Figureheads:
1. Eric Statue
2. Quetzalcoatlus Statue
3. Poseidon Statue
4. Danu Statue
5. The Angle Statue

Captain Abilities:
For the long range ships, Quick Reload is the skill to go. This skill will increase the fire rate of the ships making them even more dangerous.

Crew:
Make sure your gunners have Penetration and Quick Reload so the damage will be even higher and faster. Alternatively you can use gunners with Penetration and Hit Rate to have more precision.

Cannons:
The best cannons to use here are the vulcans. 6 vulcans and 1 smoke are the best combo you can do. The vulcans will deal a HUGE amount of damage to the main target AND the sorrounding enemy ships, and it will set the ship of fire causing more damage over time. The smoke cannons will blind the enemy reducing their damage and helping the other ships of your fleet.



The stunsails improve your ships speed while sailing in the world.
The choice is between a spanker that gives you more speed when moving in the direction of the wind or a spritsail that gives you more speed when moving against the wind. This is mostly a personal choice and doesn't influence the combat at all.

The Minos Maze is located just south of Chania, but to enter you need to get the key from Azuchi Castle in Japan.

Once inside, you need to use the keys wisely or you won't be able to get the best rewards at the last level.

First of all, when you move around, try to find alternate way without opening the doors. This is very important because the keys are precious.

Second: once you get the first silver key, go back to level 1 immediately to get 6 more from the locked room.

Once you have all the silver keys and the gold key, DO NOT use them until you beat the boss at level 10.

When the boss is dead, you have 2 rooms with a gold chest in it:
- Right room: the gold chest contains blueprints
- Left room: the gold chest contains random loot.

First get to the right room and take the blueprints, then open the silver chests around. If you are lucky you might get another gold key. If not, go back 1 level and open the room with the level 7 skeleton and see if that silver box gives you one.
If you get a second gold key, go open the last room at the last level, otherwise, you can just use the silver keys randomly to get some materials.

NOTE: Level 7+ monsters can drop Avenger and the Pope's Robe, so don't leave any of those behind.

In this dungeon, you have to escort a ship along a path marked on the map. During the whole time you can't stop to repair or fish to recover food, so you need to be prepared.

The first thing you need is a fleet of strong ships with few sailors in it. The best combo is using the Ragazzoni Sailbot + 7 Turtle Ships, with minimum sailors and 2 sailor heal and a couple of repairs.
Make sure you have at least 50 days of food before going in.

When a combat start, heal your sailors as soon as possible and take down the enemies. Don't be afraid of high level enemies, since they are undertuned (or it would be impossible).

In the map you can see big X and smaller ones. The big ones is where the escort ship will stop and be ambushed. Clear the ambush as fast as possible and with the remaining time (visible on top of the escorted ship), go around to the other small X. There you will find items to get some boost, food and the sailors restock.
After each battle remember to go into your fleet settings and split the sailors amont your fleet by using the "auto" button.

Remember that you will be rewarded only if you successfully escort the ship to the end. If you fail all the loot you get is also lost.

The GM Fleet is a world boss that roams around the isle of Imoban in South America.

To defeat him, you just need to use a normal fleet that can handle level 16 pirates and you'll be fine.

Other than the usual loot, GM Fleet is the only one who can drop the Eric Statue, which is very good to increase the raw damage of your melle and ranged ships alike.

Prince Theseus is a world boss that can be found near Chania.

To kill him, you need 8 RANGED ships, all equipped with exclusively mortars (the bigger the better).
I suggest you to use ships with a good amount of sailors to survive his mortars attack.

When the battle start, make sure to use 4 ship on one side to attack 1 enemy ship and 4 in the other side to attack another. Two groups of ships taking 4 on 1, can melt his entire fleet (with some luck with few losses).

NOTE: farming Prince Theseus is a good way to make money and level up crew members (it takes 5 to level from 1 to 60).

The Leviathan is a world boss that can be found in Europe, Africa and Asia.

This boss is not very easy to kill at first, but here is my strategy:

1. Take 4 MELEE ships and 4 RANGED ships, equipped with at least 3 repair (4 would be better), 2 quick reloads (for ranged ships obv) and increase morale + conflagration for the melee ships.

2. When the battle start, move 2 ranged ships and 2 melee ships on the top-left of the boss, the other 2 ranged and 2 melee on the top-right. (make sure there are 2 repair per side, or 2 and 1 if you only have 3)

3. Move the ranged ships away from the boss attacks while it moves, and keep the ships in position until the blue bar is at 0.

4. At this point the boss starts to blow everything up, so you need to move the ship wisely to dodge the explosion. The explosion spread like a pentagon as you can see in this picture.

Any ship in melee range will take the damage no matter what, and in the end only your ranged ships will survive (unless you can move all the ships well, it's possible, but hard to do it).

5. Once you find your switspots for the ranged ships (like on the picture), don't move the ships anymore, the boss will just chew on the closest one and try to blow them up (and miss). The bite damage is manageable with the repair, and you can simply wait like there spamming the ability until is dead.

NOTE: if less than 4 ships remains for the final attack, it will take longer and longer, with only 1 ship is doable but it will take like 30 minutes or so... if you follow the strategy correctly you will win in about 2 minutes total.

Leviathan Locations:

Europe:

Africa:

North America:

South America:

Poseidon is a world boss that can be found in Asia.

Poseidon deal damage to sailors, not ships, so using a fleet with a high amount of sailors is the key to taking him down.

<At the moment I haven't figured out a tactics to take him down, I will update the guide when I find it>

Poseidon Locations:

Asia:

South Asia:

Siren is a world boss that can be found in the Pacific Ocean.

The Siren deal huge damage to ships, so having a fleet with high armor (Ragazzoni Sailboat + 7 Turtle Ships) is the key to take her down.

<At the moment I haven't figured out a tactics to take him down, I will update the guide when I find it>

Siren Locations:

South Pacific: