BEST way to use Linux Host's GUI applications on Windows VM

It’s known that X11 Forwarding with Windows-side X11 server is not that fast at displaying fast-updating GUI.

On the other hand, for VNC or XRDP, it’s not possible to use seamlessly.

If I use Linux’s GUI applications only for things like non gpu-accelerated apps like dev tools, is it best to just use X11 forwarding with virtio-net host only network? Is there any other more appropriate(fast) way?

If you are trying to use the X application transparency, then you need to use something like Cygwin or Mingw to pass the application through ssh. That is the only way that you will get a “seamless” window. Anything else is just video rasterization. Unless you are using an application that has fast refresh values or utilizes GPU acceleration, you should be fine. It all depends on how fast the “network” is. In this case, it depends on the overhead of how you setup you network in qemu/libvirt

If you are going a one off application that doesn’t require acceleration, I do SSH forwarding with SSH compression. The compression is important. It really helps latency because X transfers the graphical data in bitmap format that is normally huge and compressible.

If you are looking for a full desktop remote session, I would look into X2Go.