I LOVE Proton. About 85% of my Windows games just... work. And probably 75% of the 15% that fail initially only require a little tweaking to make work. My only complaints are that steam uses arbitrary numbers instead of human readable labels for emulated AppData folders. It can be time consuming to locate a save game file. Also Streaming cross platform isn't a pleasant experience yet but it's getting better and I rea…
IIRC, the folders that contain a Steam UserIDs save game data are named after the game's Steam AppID. You can look them up here (https://steamdb.info/apps/). I admit it's certainly not a solution to the discoverability problem when navigating a filesystem, as there are over 100,000 AppIDs and growing at this point.