From their readme:
Things it contains that Valve's Proton does not:
- Additional media foundation patches for better video playback support
- AMD FSR patches added directly to fullscreen hack that can be toggled with WINE_FULLSCREEN_FSR=1
- FSR Fake resolution patch details here
- Nvidia CUDA support for PhysX and NVAPI
- Raw input mouse support
- 'protonfixes' system -- this is an automated system that applies per-game fixes (such as winetricks, envvars, EAC workarounds, overrides, etc).
- Various upstream WINE patches backported
- Various wine-staging patches applied as they become needed
- NTSync enablement if the kernel supports it.