Been running the latest production builds since I built this sig rig almost two years ago. 4 feature updates, went from 2 1080s to 2 1080 Tis, swapped out the 3 1080p 3D monitors with a better set of 1080p 3D monitors, added two VR headsets, a 4k monitor and an additional 4 TB of app storage. I've never plugged this amount of hardware into a PC with this amount of software installed running prior versions of Windows but I don't see how Windows 7 or 8.1 would handle this setup any better, especially when dealing with 4k.
It isn't a question of what it can handle, really none of that is win 10 specific. My beef with Win 10 is the removal of Group policies from Pro, the forcing of or at least making the removal of anything related to the store extremely difficult etc. My beef with Win 10 isn't performance related, it is purely features I use and paid for with Win 7 being taken from me.