March 29. 2020 edit: Recently I published a tutorial using Virtual Machine Manager. You can find it here: Creating a Windows 10 VM on the AMD Ryzen 9 3900X using Qemu 4.0 and VGA Passthrough.
Before you get your hopes high, this post is not (yet?) a tutorial on creating a Windows 10 virtual machine using the Virtual Machine Manager (virt-manager) GUI. It should have been, though. I spent the better part of a week trying to configure and install a Windows 10 VM that delivers the performance that I’m used to.
As it turns out, it was a failure. Don’t get me wrong, I did manage to configure and run Windows using virt-manager and virsh. I even installed it multiple times, changing the configuration to what I hoped would improve performance. But whatever I tried, I never got even near the speed and snappiness that I achieve by following my tutorial using a start script.