Mint and Debian are great, and once you set everything as you like it, they’re pretty solid. Pop_OS is easy if you have an Nvidia GPU too.

As for comparability, proton has all but settled the issue. The SteamDeck runs on Linux after all. Take a look on Proton Database to check if a game works well or not. FWIW, every game I’ve tried save one has been flawless, and that one did things with files and wallpapers.

If you have a second computer you don’t need working, I’d recommend just trying something on it, switch distributions now and then. See how far you can get with just Linux.