a windows OS mode that is single user, networked, and meant for limited use (so background housekeeping windows tasks run after you exit or reboot out of this mode) would be pretty ideal, not just for raw performance (which would be measurable, but not the main goal) but to avoid apparently random decreases in performance due to Windows deciding to do something, or suddenly needing to deal with an authentication request dealing with mapped drives, or something.
Basically, Windows needs a "Game Console Mode".
If you want to get super crazy, I'll boot a second copy of Windows off of a vhdx file that's stripped down if I want extra performance.
With a little bit of work you can even clone the sid of your main os, and symlink most of your existing files and info, so it's almost identical to your main OS.
Calyp.to's guide is one of the best I've seen for stripping windows down to reduce latency.
https://docs.google.com/document/u/0/d/1c2-lUJq74wuYK1WrA_bI...