I have index and 2080ti also.
there are two sliders in steamVR, there is a global one in the video section and there is another in the application.
what is your global or base set too
i have been playing with global SS = 150 and elite application SS = 120
giving a total of 180% (1.5 x 1.2 = 1.8)
i have been hoping to get to global 150 and application to 130
giving a total of 195% (1.5 x 1.3 = 1.95)
it works but in stations reprojection kicks in, its ok in space. the 180% seems ok around asteroids also. I haven't tested asteroids at 195%
i also leave in game SS to 1.0 and HMD IQ to 1.0, it does seem to perform better with steamvr SS rather than in game. I need to test to confirm, and I'm not sure if image quality is better or not. I am ok running at 80hz rather than 90 which gives a few mill seconds head room
i do have shadows and Amb Occ set to Low
the reason for asking is, i got index 3 weeks ago.... and i am trying to find the highest settings which give the best quality image and performance.
i suspect i will end up, having reprojection or smooth motion kicking in at stations and not everywhere else.