The default open-source nvidia graphics driver is a bit sluggish at 2160p, and more sluggish at 2x 2160p, but it'll do for now.
Also sometimes I have to reset the 200% scaling on my monitors, but that's probably because my monitor has crappy firmware. But I can now do that through the GNOME Settings app very easily, instead of manually running a command like I used to have to.
Seems to crash the display server when the screen dims after idle. Whoops! Also it turned off wifi when turning the screen off, which is .... not good for an unattended vagrant setup that needs the network, either of them. :(
The wifi-off option can be disabled, and for now I'm just going to explicitly lock the screen when I want. :P