For testing, I would change every ultra setting to high, and every high setting to medium.
100/100 tlod/olod.
All these are just for testing. You can always raise them. The object is to get settings that give you as close to stutter free results as possible and then build on that.
You could also use x2 FG as an initial starting point.
Here is one thread on Fauna if you are interested. Not just for VR. 2D also.