I'm running PT 9.5 on an M1-based iMac with Parallels, and haven't seen this sort of problem. It is a bit slow at times, but doesn't have visual issues like that. I've been running this way for more than four years, and it's quite usable.
I would check what resources are available to the Parallels VM. On mine, I have CPU and memory on automatic, which it gives as 4 CPUs and 6 GB RAM (up to 3 GB for graphics). If you have less memory on your machine, you might want to try increasing the allocation and being conservative on the Mac side with what apps are running.