To me, it looks like you don't need a 3950x, or a 3900x.
I bought a 2700, and while using resolve, running 3vm's and a bunch of background tasks I'm hard pressed to keep the CPU stable at 100%. Don't get me wrong, it will spike there for a second or two at a time, but it wont hold 100% constantly.
Maybe a 3900x would be useful if you setup a VM for a Plex server, and another for PiHole or something.
EDIT: CPU usage other then rendering video...