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.
DXVK is not “Proton’s fixes”. It exists as a separate entity whose development Valve has helped fund and who Valve devs have directly contributed to.
Proton’s fixes are out-of-tree tweaks to DXVK, Wine and VKD3D that, put together, make games work much more seamlessly and smoothly than they otherwise would.