I am running an I7700k OC to 4.8, 16 GB ddr4 3200, Nvidia 2080ti and a Valve Index at 200% supersampling. My usual fps in multiplayer is ~45 fps, decent image quality (for VR).
My recommendations:
Remove ground shadows, remove MSAA and set Object Distance Draw to medium.
I was using a Pimax 5k before and it requires a lot of computer power (one of the reasons I am using an Index now) it is the price you pay for having the huge fov. Be sure of enabling Fixed Foveated rendering and disable Parallel Projection.
I am 8KX backer and honestly, I don't think I am going to use it for DCS unless Nvidia releases an incredible graphic card this summer.
By the way, the HP Reverb looks awesome and runs at 90 fps, maybe you can borrow one to test.