Actually you can run Windows through Qubes, but I would not do that. Theoretically the Qubes VM capture the client OS, but you might never know when due to some vulnerability it can escape from the virtualized environment, and knowing Windows how full of bugs and shit it is, I would not risk that.
But you can run pretty much all Linux OS-es in Qubes and it already comes with Fedora, Debian and 1 other preinstalled and preconfigured, as a template.
It's pretty cool, but Qubes is missing some drivers so those need to be configured as well.
I have installed Qubes in the past on an older Lenovo laptop and it didnt had the graphics driver configured well and the screen was black and white with stripes like on old TVs.
So Qubes definitely needs more work, that is why I said in the article that it's relatively new, but this was like 1 year ago, maybe they have fixed it since.
In any case once Qubes gets all bugs fixed it will be the best and most secure OS out there.
But until then I'll just stick to Debian on my cozy AMD machine.