I’ve got about twenty hours on the deck so far, it runs perfectly fine. You can literally just use the “Steam Deck” in game preset and lock the framerate to 30 and it’s playable. The tweaks people post guides for are to make it run a little better or look a little better at a higher fps, but if you’re happy with 30 then it’ll run at a relatively stable 30 if you do what I just said.
I bought a Steam Deck and I’m actually selling my PS5. Everything I played on PS5 runs perfectly fine for me on the deck (I don’t mind 30fps), so it was a pretty good choice for me. Just takes up less space, and I still dock it to the tv.