I don’t know the specific needs for the programs you are going to run but 3.4ghz and 6 cores for each vm is a good amount of processing power. Ram is going to be your limiting factor. How much ram is the server configured with? Windows is going to want a decent chunk Linux is usually lightweight enough and just needs what the application will need.
I’m using a Dell r720 with 2x Xeon E5-2690 and 128gb ram. I am running xen community with a ton of Para virtualized Linux boxes, matrix, jellyfin, airsonic, next cloud, DNS, photoprism and more stuff and I’ve got a decent amount of CPU and ram overhead