I'm a fairly casual gamer these days, but nonetheless it's been a very long time since I encountered a game on Steam that wouldn't run at least tolerably well under Proton, with most of them running flawlessly. As long as you check the DB before buying, you're fine. As you say, it's only really the anticheat software which causes major road blocks most of the time.

Performance is amazingly better on Linux via Proton than it is on Windows quite a lot of the time. It's an incredible achievement.

For non Steam games, Lutris also provides as easy, one-click experience for getting many games working, and although I don't have a lot of personal experience with it (Steam covers most of my needs) when I have used it it's been a pleasure, and it has a good reputation.

I use bog standard un-tweaked Ubuntu. One would assume that the performance on the specialist gaming distros may be even better still.