I love my steam deck; but I installed windows on it and never looked back. You linux nerds can scream and cry all you want but setting everything up on windows is just objectively easier. Yes, there are a lot of nice features I enjoy about SteamOS, like TPD control, CPU and GPU clock speed controls, etc; but many of those can be done in windows as well. Steam Deck Tools says hello.
Try running a game with Lossless Scaling in SteamOS. You just can't. Want to play a game with mods? You can probably forget that. Want to install literally anything that doesn't come from Steam itself? Gets complicated fast.
The negligible gain you might get from using a lighter weight OS like SteamOS could easily get eaten up by a proton compatibility layer. For me, the absurd amount of control you get from switching to windows is worth far more than the meager offset of a few extra frames.
SteamOS can be a beautiful experience. It's a very tailored, console-like experience, and I think if you just want to play Steam only games, it can be a wonderful time. The moment you start to complicate the process at all it falls apart very quickly, and if you're not familiar with Linux, it can be an ugly mess.