Krunch from over at rooz shared his vr gfx settings, he has a gtx1070, I set mine similar with maybe a couple things a bit higher (1080ti-lenovo hmd) and runs smooth 60-70fps;
Things that helped make the game run more smoothly in my Rift and still not look too blurry are:
- Resolution Scale reduced to 70%
- Pixel density in-game Raised to 140% (this may have a different effect on your HMD)
- Locking on ASW (so game runs at 45fps but still get 90 in HMD)
- Temporal AA on high (don't go lower)
- set the car LOD quality to the lowest setting
- turn off dynamic sharpening
- set the sharpening slider to something that works for you eg 200%
- find the right level of other settings for your system Eg lower mirror quality and number of visible cars, but maybe get shadows up to med or high
- don't mess with engine.ini tweaks unless it's as a last resort
Check out the VR threads in the ACC forums (login needed):
https://www.assettocorsa.net/forum/index.php?forums/acc-virtual-reality.83/