Decent, with proton I can play most games with no issues

A large majority of games on steam work via proton.

For games outside steam, there's a pretty good community around wine wrappers. I think it's called lutris.

I used to play GTAV, assassins creed, and other AAA titles through it 4 years ago and its only gotten better.

For single player, the majority of games should work just fine. Most gaming issues nowadays are either because of invase DRM or anticheat, but more and more games are getting support. A large part of it is thanks to the steam deck.

Surprisingly good. It's no longer that depressing list of the same handful of open source games. These days you can be fairly confident most games will run OK, especially if you're running Steam.

Through Lutris, really good