nividias AH dx 11 profile, turn off everything, everything v sync included.
game video settings, use a smaller screen res 1200x800, 1K or 2K text settings, disable v sync.
graphic settings, disable all, especially post lighting, run the terrain detail sliders down a bit.
No graphic settings help the clarity, they disrupt performance. I also uninstalled the tray tool, not worth the perf hit. Once in game I turn off all other displays.
the other thing was to use a frame cap at 93f/s. No point churning the card. The rift is 90Hz.
so far crowds no bother.
luck