Switched from the Oculus version of the game to Steam as I really wanted to purchase the DLC and the game was 70% off on Steam. Took me a while to get performance parity with the Oculus version, even with the same settings. The scale of the HUD / UI elements was out of whack, and VR view was mirrored in fullscreen, and alt-tabbing to check on my system would stop me getting back into the game. To fix this I did what was suggested in this guide, but a bit differently, updated C:\Users\<you>\Documents\My Games\DiRT Rally 2.0\hardwaresettings\hardware_settings_config_vr.xml and set fullscreen="0" - this put the mirrored display into windowed mode and also fixed the scaling issues with the HUD. You can even copy over the hardware_settings_config_vr.xml from "C:\Users\<you>\Documents\My Games\DiRT Rally 2.0 Oculus" so you end up with the exact same settings as you had when playing the Oculus version.
I disagree that the night stages and Sweden look bad - I think they look amazing! Sweden in the snow is really hard to follow, exactly like that time I drove through a snowstorm 🙂 I get a solid 80 frames with high shaders with my 2070 RTX and the game looks incredible. I do see frame drops in areas with lots of buildings (ie: the towns in Spain)