OK update time: After I clean reinstalled the latest NVIDIA driver (though I was already on it) and rebooted it's finally working at high refresh rates. Running on an i7 8700K@5.0GZHz and a 1080Ti and I need to run at 100% SS and 90Hz with my Index and all VR in game settings to low for it to be playable. V-sync disabled of course, but it doesn't seem to matter whether or not the mirror screen (external monitor) is full screen or windowed as far as performance. What's interesting is even though I have motion smoothing fully disabled and legacy reprojection disabled, there seems to be some sort of built-in reprojection in the game that when it detects enough frame drops goes back to the doubling caused by the 60Hz limit issue. If I raise all in-game VR graphics settings High it behaves pretty much like it did before with the ghosting/doubling of everything when I turn the ship. If I reduce it to Medium it fluctuates between perfectly smooth and no ghosting, to ghosting when things get intense.
I have to say even with all low settings and finally mostly smooth frame rates at 90fps my control of the ship and aiming with my HOTUS is much improved and more responsive. Seems the 60Hz issue introduced more input delay that I thought, but this is awesome.