I am using Crossover on Qubes 3.2. I suppose that it have to work fine in Qubes 4.
You just have to install it and register on the template VM, like any other software. After that you can install the Windows apps in the App VM because they are installed in the user home dir
I once was a hardcore lock-in'ed on MS-Office products too, but at one point, I decided to write a major paper entirely on LibreOffice. I learned a great deal in the process. Putting it short, you can get past your MS-product addiction, if you push through it.
However, it's true some aspects of the MS-products still prevail, for example the difference between Calc and Excel, is a massive headache, considering how much each of them can do, and do in such a different way.
But if you don't use Excel, then I don't see much reason to stick with MS-products, or perhaps, you got some reason I overlooked?
I once fancied the aesthetics of MS-Office (and I still do), but after growing used to LibreOffice, I don't care much anymore. The aesthetics are still nice and all, but it's just not as important as it was before.
Perhaps you can use some of these thoughts, or perhaps you got valid reasons, whichever is the case, I hope you find your sweet-spot.