Launching DCS in VR mode with MultiThreading was failing, with it locking up in the loading screen.
Like Lobo says above, updating my OpenXR Toolkit to 1.2.4 seems to have fixed that issue. After updating that, I can now run the Multi Thread version, using PimaxXR and OpenComposite. My headset is a Pimax 8Kx.It launches and I made it into a MP server as a test. It does seem to have increased framerates some. I noticed that when running it in MT mode with the frame rate counter on, there is now a message on the frame rate counter that will say either CPU bound or GPU bound. When in game, on Grayflag PG server, sitting on the ground in a cold Apache, it was quickly alternating between those two messages.
However, it is unplayable due to head tracking issues. Can't really describe it well, it seems that when in MT mode, headtracking is having problems. Seems to be stuttering or fluctuating somehow. It was bad to the point where I had to pull my headset off to avoid motion sickness.
To verify that the tracking problem was related to MT mode, I then launched DCS in normal VR mode, again using PimaxXR and OpenComposite, and everything was fine. Head tracking was solid.