If you are using DX12, please revert to DX11. DX12 is currently in the process of performance improvements being made by Asobo in SU10Beta, which will be released soon. Asobo is stuck until new drivers are available from nVidia, especially since there have been issues with nVidia GPUs.
DX12 is almost never a winner, especially in a VR environment with SU9.
SU10 is a work in progress and its behavior changes with each weekly upgrade; DX11 is (as of today) safe.
I personally believe that it is hard to reconcile the two when it comes to FPS and stutter and that many people tend to go for stutter reduction because the FPS does not increase much in MSFS.
Performance must be improved first, as VR will never perform better than normal display modes. I think the Oculus specific issues come after that.
The settings seem low enough, but try once moving the google maps extension from the community folder to something else and not loading it, just to be sure.
I don’t use these mods, but depending on the graphics format, the large VRAM hit may slow you down.
Also, try flying with the rolling cache completely removed once. I have no clear evidence, but it may change the behavior.
As for the main thread limitation, keep in mind that this is only in Dev mode. This does not mean that someone is limiting your PC, it just shows you where the performance bottlenecks are.