Hiya,
I’m sure someone else will help with specific diagnostics as to the root cause, but if it helps, here are my current stable settings:
I have a pretty similar rig to you, you should be getting playable results with a 2070.
I’m sure you’ve read it all before, but I strongly suggest you try and get to a stable FPS so you know your base line, then push settings up from there.
I went around in circles, got everything stable, then pushed the boundaries too much (FS2020 graphics and too high super sampling in Oculus) and things went down hill fast. Returning to these settings gives me stable results and I’m slowly tweaking further to see how far I can improve.
edit:
Sorry, I missed a part of your original post. You’ve clearly tried similar settings.
Sounds like a Link issue, what result do you get using Device > USB test in the oculus desktop app?