Source is this video:
Windows Was The Problem All Along - Dave2D
We could obviously compare performance between windows and steamOS before on the steam deck, or between windows and Bazzite on other handhelds. But this is the first time we have had official windows and SteamOS builds for the same hardware.
I’m not sure what you’re saying. Proton is incredible obviously, but by itself it doesn’t make games run better. Using vulkan instead of DirectX could improve performance, but presumably most of the performance gain is from not running windows in the background.
It’s a bit of both, along with the Linux AMD drivers being superior in many cases to the Windows drivers.