Documented the recommendation here explaining why virtio-gpu is used and noth qxl which is obsolete:
VGA and other display devices in qemu | 🇺🇦 kraxel’s news [archive]
According to Gerd Hoffman (libvirt dev) vhost-user virtio gpu is the ideal mode for performance and security but this is only available as of QEMU 4.1 which came after the Buster freeze[5] Libvirt support is also pending.
QXL has been superseded by virtio-vga where most development happens (and security attention probably). 2D acceleration as a distinct mechanism is outdated and 3D mode is where all types of graphical acceleration will be handled:
" This device has support for 2D acceleration. This becomes more and more useless though as modern display devices don’t have dedicated 2D acceleration support any more and use the 3D engine for everything. The same happens on the software side, modern desktops are rendering with opengl or vulkan instead of using 2D acceleration. "
@onion_knight if you see everything works alright that’s ok with me.