Did you find a solution? I am struggeling with my Reverb G2, 6900XT (from 1080), 3900X and 32GB 3200 ram
Low framerate and high frametime in Iracing
I have not experienced the frame drops since I disconnected my second monitor (and use only 1 144hz) and turned off the steamVR chaperone completely. Thought, sometimes there might be some drops but they are so rare that I have not paid any attention and considered the matter resolved.
5800x - 6900xt - Pimax 8kX and for me its just that reprojection / motion smoothing are not present. It doesn't lock to 45 fps when 90 isn't maintained, or lock to 36 if I'm running in 75hz mode or lock to 30 when running in 60hz mode, It just struggles to make the full refresh rate, and fails, and becomes a stuttery jittery mess the entire time, and even when it does make the full refresh rate, there is still constant microstutters. I did not have this problem with the 1080ti. The Nvidia 1080ti ran reprojection perfectly fine, and even though I only got half or less then half the FPS the experience was smoother and better.
I talked to SteamVR support about it, and they blamed Pitool/Pimax, I talked to Pimax about about it and they blamed the AMD driver. 3 AMD driver updates have come out since I've personally been experiencing this issue, none of them have made any difference at all. If it isn't resolved in the next update I'm going to sell the 6900XT and try to buy an Nvidia RTX 3090.
I figured this out by accident.
with my 6900xt in DCS there is no reprojection, its just a suttery mess. However if I Alt+Tab to make DCS not the selected window I can still look around in DCS and its butter smooth, but when I select DCS back as the main window again, its back to a stuttery mess.