I have a Rift S also, and what worked for me was to not use Oculus Tray Tool. just straight Oculus app, and start MSFS, and use the Render scaling to increase the resolution.
So far this is giving me the best results. I was having very poor image quality, no matter what Oculus tray tool settings i was using.
i9-108500, EVGA 3090, 64GB DDR4, Rift S. Most texture settings on ultra, AA 4x Render scaling 170, BLoom off, Water low, most other settings medium to high.