Game Content and Flavor
Historical Events Extended
More Shipnames Mod
Rosetta
Sailing tradewinds
Ruler Titles
Contest Europa
Armies Reworked
Recolored Nations & More Shipnames Mod Compatibility Patch
This updates Recolored Nations for 1.17

Game Mechanics
New Forts
Institutions Reworked
Ruler Traits Lite
I use this mod without the Randomizer or the Muscovy buffs options
Sea Change

Pre 1.18
Westernization Reworked

Ideas
The Idea Variation (This really straddles the line between ideas and mechanics because the new idea groups really provide a different experience. I use a local version with a small edit to change some of the core creation cost increases down as I find them to be overpowering)

Culture Conversion Mods
Dynamic Culture Conversion
Organic Culture Transmission

Cultural Diversity Mods
Zucklov's Cultural Diversity Lite
Reworked Cultures
Remade Cultures 1.16
Note that Remade Cultures 1.16 is fully compatible with Organic Culture Transmission but isn't fully compatible with many other mods, including Contest Europa. I'm hopeful that a fix is in the works.

Culture Compatibility Mods
Patch for Contest Europa and Reworked Cultures
Patch for Contest Europa and Vanilla culture

NOTE: If you are using Contest Europa then you MUST use one of these culture set ups:
1) Reworked Cultures AND Patch for Contest Europa and Reworked Cultures
2) Patch for Contest Europa and Vanilla culture
Do NOT use any other culture mods as they are not yet patched

General Graphics
A Revolutionary Borders Mod
Note: this mod has a lot of options so you can customize as you like, just ensure you download enough parts
Arms Spaghetti's Alternative Shields
Vanilla Loading Screens with Information
Readable Exploration Missions
This mod is not updated for 1.17. I have a local version that I have updated.
European Advisor Portraits
Monster Incognita
Immersive Advisor Portraits

As a general rule you can use whatever graphics change mods you want, there won't be any issues except between the graphics mods themselves.

I've made my own graphic mod by combining various parts of other mods that I like, you can do the same.

Unit Models
Breese's Unit Models
Gm_Kaiser's Unit Models
Horsemen of the Crescent Extender Lite
Jerusalem Crusader Knights Unit Models
Unique Japanese Daimyo Units
Dynamically Colored Manchu & Thai Unit Models

Flags
I use a custom combination of content from the following:
Flag - Polish-Lithuanian Commonwealth
Japan Naval Ensign (1889)
Leo's Flag Pack
Byzantine flag with double headed eagle
A Revolutionary Flag Mod
Romanov's Imperial Flag
Asian Flag Quartet
Fancy Flags

(This means I have created my own mod for my local use using a combination of content from these mods. You can do the same by copying and pasting the flags you want into a mod you make)

Religion
EVE Religion Lite
Contest Europa Religion Addon