Valve seems to be testing ARM64 and Android support on Steam, as per a new SteamDB leak. Popular titles like Left 4 Dead 2 and Garry's Mod are being tested with "proton-arm64" tags, among others. This could hint towards new future Valve hardware running on ARM64 architecture.
An iffy game library? It runs almost everything that isn’t an online game with certain anti cheats. It’s pretty not iffy at all.
My Steam Deck plays a lot of games, more than I even expected it to. Honestly I’m not sure where this “iffy library” crap comes from.