Graphics card is fine. Qubes barely uses it (it only runs dom0 graphics). Graphics in the qubes is handled by cpu. I have some ancient cards and they are fine. I do get that mouse stutter issue on my older desktops but it seems to be I/O related (occurs when sys-usb is heavily used). My newer desktops have no stutter but are just using iGPU.
Video esp high quality has issues on qubes. There’s a recent thread on here about it. You could put in a 5090 and it would still be there. Up the vCPUs and memory on the relevant qube