Disable/turn off all of the Win10 Gaming settings, and disable xbgm(xbox game monitoring) in task manager(services). Also windows 'Fullscreen Optimization', can be disabled in a games exe. properties(can affect some games behavior).
Depending on how much fat you want to trim off win10, https://www.tenforums.com/
Should now show as disabled.
Not sure why yours is greyed out (I'm still on build 1709 pro vers.).