"Ah, you're using this kext hack mentioned before. Yes, NVIDIA drivers will work in this case. It's just that we cannot recommend a hack, especially if system security must be weakened in order to use it."
Just to be clear:
In my Primary install of Sierra 10.12.6 with System Integrity "enabled" for everything, NM in 4.0.3 does not display anything but the window outline.
I installed a separate copy of Sierra 10.12.6 to a separate drive to test the kext hack, and NM displays/functions as I expected (based upon how I see it work on my 12,1 MBP).
What I found interesting was that--this week--I installed a fresh copy of High Sierra to an entirely separate disk, installed the nVidia web drivers with System Integrity "enabled" for everything, then LS, and NM in 4.0.3 displays as expected (albeit w/flicker) . . . no modification of System Integrity, after-market kexts, etc.