Have been testing this on an up to date Debian Buster host system. One issue regarding the video driver for the Workstation. Default setting is for Virtio, but when I use it, it creates a lot of artifacts on my screen during scrolling or moving a window. This creates usability issues. In an older Whonix KVM 15 release, the video driver was set at QXL. I had no problems with QXL, so I edited the Workstation XML file for 15.0.0.7.1 and switched again to QXL. The artifacts disappeared. Why was the video driver switched from QXL to Virtio? Am I running a security risk using QXL versus Virtio?
Strangely my experience is the opposite. Do these artifacts still appear in fullscreen mode? Could be the code is not playing well with your video card.
This device is where all future features, performance and security enhancements will be made. It is designed to bemore secure than QXL already. QXL is essentially abandonware at this point, but I am sure upstream will fix any vulns discovered. However most eyes will be on the default recommendation which is virtio at this point.