I'm going to make this stupidly short as I have written a huge post three times now only to watch the page go white and all my typing disappear.
System: i7 3820, 32GB, 1070 ti, evo SSD, water coooled, etc.
things ran great and then suddenly they didn't. everything a laggy mess overnight and I tried every fix i could find online. I found the fix by accident. it will probably only help a very small percentage of you, here's hoping:
If you are using the oculus beta, with the pull out windows enabled, check if windows is scaling above 100%.
I think windows had asked me if I wanted to fix blurry apps or something one day, i clicked yes and thought nothing more of it. eventually found that it was scaling the "monitor" that is created by the oculus beta experimental setting to 120% and by simply turning it off, it fixed many many hours of internet investigating, formatting disks, driver replacements, and so on. on fresh installs of windows, it was restoring my saved settings; as Microsoft do. I went from unable to play beat saber, to 4x supersample on almost everything with high settings. I have yet to see this mentioned anywhere else, so I hope some of you find peace. 😄
Oh, I was also able to fix the in-game problems (temporarily) by ensuring something (ANYTHING!) was on top of the mirrored window. I would open windows stickynotes, shrinking the note as small as possible and put it at the top right of my tv screen, in "focus" (on top of tall other apps, and most importantly, the game) amazingly, this would fix all frame dropping problems in the HMD, and people spectating wouldn't even notice it on a 100' screen.