I often experience the same problem, and I suspect that it is a bug in the graphics engine of DCS, as it appears to happen only in DCS. Note: I think that it happens to me while in Syria and flying the A10CII. If anyone has any other suggestion please shout. My system is a 9900K + 3080FE + 32GB + nVME.

It's a shame cause I really like TacView. Turn off TacView, which would otherwise be recording thousands of parameters of all the objects in the server. It's not as straight forward to do it though. Turn off the Guardian on Quest 2 as apparently it takes a bit of CPU power, and CPU power is precious. So far I've done two things that seem the delay/prevent the occurrence of these fps drops: They occupy the bottom ~10-15% of each eye and they drive me nuts! After alt+tabbing (and doing all the things to bring the performance back up) these shaded areas annoyingly persist. I also noticed the existence of a 'shaded area' on the bottom of each eye, sometimes only on one, after the fps drop hits. I have exactly the same issue, using Quest 2 on a crowded multiplayer server, all going well until I'm hit by an horrendous performance drop with tearing all over the place.

Virtual desktop frame drops