There is a lot of stuff the tutorial doesn't cover properly, so here you are some generic tips and tricks to get started:

• if you can consistently outmash your opponent, go full speed ahead, because they won't stand a chance at winning the mashing minigame, unless they use Twain with his passive skill on [only available in the full version] OR they outplay your mind games
  
• if you are consistently outmashed, buildings and mobility are your friends. Mashing doesn't help against a fast moving skyscraper thrown in your direction
  
• if you rush an opponent, you can end a clash with a throw instead of a punch. This can help if the opponent is better than you at mashing
  
• the first recovery prompt is almost unuseable do to it being very fast, so a follow-up attack after sending the opponent away is almost guaranteed (unless the opponent is using Groovis and his Avoid passive skill is active)
  
• doing nothing during a clash triggers the Taunt. Taunt wins only against Counter, and gives the taunting player full meter and a free attack. As risky as it is, it is another level of mind games

Concerning the various characters, while the statistics are the same for every one of them, each one has a different passive skill (which triggers after a certain time or if you have been dealt enough damage) and active skill (the super move):

• Armoir has a super with gigantic hitbox and his passive skill makes you deliver a full power punch at the next clash, no matter when you press the Attack button. This punch will overwhelm any normal Attack (even on the same intensity), but will lose against Counter
  
• Shin's super is a 270° kick with short range but doesn't require aiming. His passive makes him faster than anything else, which makes it easy to throw buildings at full speed or catch a recovering opponent
  
• Skelly's super has a decent hitbox and her passive makes her throw four bones in different directions at regular intervals, thus disrupting the opponent's approach (NOTE: originally, Skelly's passive was MASH, which helped her win easily every mash contest while it was active. This skill is associated with Twain in the full version. Since the update 08.06.2020, Skelly's passive is aligned to her version in the full game)
  
• Groovis's super has a very small hitbox and needs precise aiming, but it's almost instant. His passive makes him auto-tech when thrown away and improves his survivability to death QTE

Mashing is a main component of this game. If you are outmashed, you will be at a striking disadvantage against your opponent. Currently, there are players reaching up to 15-16 clicks per second on either keyboard or mouse. One way to check your mashing speed is to use this (non-affiliated) website here:
https://www.shmupspeed.com/
To get your clicks-per-second, just divide the result by 10.

If your mashing speed is slower than 10 clicks per second, you might want to follow some tutorials on how to mash faster. One of such tutorials can be seen in this YouTube video.

If you are consistently outmashed, stage knowledge, throwing objects, careful teleports and positioning can help you get the upper hand, even though it is definitely an uphill battle.