I've been thinking about this a bit, and overall the categories seem pretty ok.

Character specific leaderboards can be accessed by clicking on their name in the filters. It's basically a couple of extra clicks in exchange for making the category list less cluttered.

The biggest downside is that there's no way I can see to direct link to these filter based character leaderboards. Maybe there's a workaround I don't know about?

Being able to see all the characters on the same list might be kinda interesting since it immediately highlights which characters are the fastest without having to click through them all. That feature would be gone with separate categories.

I believe multiple submissions per user should still work properly. Like if you submit a Floyd time and then submit a faster Adam time, both should still show up on the leaderboard. It shouldn't obsolete slower runs unless you use the same character.

At the moment the only thing I'd suggest is moving boss rush from a category to a difficulty, for no reason other than because this would probably fix the 2P Character appearing in the filter list twice.

Other than that I wouldn't mind leaving things alone to see how it goes.

Delete all the extra Characters, Character 1P, and Character P1 variables you've made for each category.

Have a single Character 1P that applies to every category (and make sure Values Obsolete Each Other setting is off) Character 2P is the only one that should be category specific.

The way you have it at the moment makes the filter menu a huge headache because every single one of those player 1 character variables shows up for every category, making it hard to tell which one actually works.

You could also check "Use as sub-category" on the variable to have it automatically subcategorise character without manually creating billions of categories. This would also make the main cast / retro subcategorisation unnecessary. *Edit: But thinking about it, this would probably mess up 2 player categories a bit so... I dunno. Just making the filter menu cleaner to use is probably ok.