I too would be interested to hear anwsers. I believe that the only proven/reliable way at the moment on KVM is to pass through a GPU although the links you post sound promising, it’s the first time I have seen them.
From my own mucking about with Windows 10 virtualised, Vmware Workstation has the best virtualised OpenGL support - good enough to run benchmarks and play games at non-to-demnading settings. VirtualBox has some support, but I found it to be basic and flakey. Microsofts own Hyper-V on Windows 10 Pro limits you to DirectX support in a VM, no OpenGL. If you want OpenGL you need to a server edition of hyper-V (and I wound’t be surpirsed if this required a proffesional, not a gaming GPU as well.)
i think that windows guest support is abandon from lastime i read about this artical the only way to get some sort of virtual gpu working is NVIDIA v gpu but on linux guest the support is kind of mature from what i read