I can pretty much just play the games I would normally, which fortunately doesn’t normally include any MMO or multiplayer only. I do play Star Trek Online on rare occasions, but it works just fine for me.
I’ve always been lucky in that probably 40% of my favorite PC games already have native ports or native options for play, but Proton has been pretty great out of the box for most that aren’t native. This year the only games I remember having major issues with were Uncharted Lost Legacy, and Batman Arkham Asylum. Uncharted was a glitch with water rendering crashing the game. It worked fine once I tweaked some settings and changed the Proton version, so it could have even been a game issue. Batman wouldn’t launch without a few different tweaks, but ProtonDB had some fixes.