I sometimes use 3d CAD software to design parts for 3D printing. Lack of 3d acceleration is one of the major hurdles keeping me away from Qubes, although I have used it and the bits that work well work extremely well. It's a very promising project.
GPU pass-through support should be as good as any other distro on Linux 4.14. You'd need two GPU's still though. If you're talking just general GPU performance in a VM, that's still not 100%, though Qubes is not involved in that work as far as I know.