Hello there,
In licensing terms each virtual copy is a running windows and must have a valid license for each instance. If you have Windows licenes than you can use a Key and activate the copy - if not you'll have to buy one.
There is absolutely nothing stopping you from using separate Windows 10 Pro licenses on a hypervisor as guest OS on a separate VM, that is perfectly acceptable. You can also access these via the hypervisor or RDP, same goes via RDP. The only mirror downside is that only one user would be able to connect to one VM at a time.
Hope this resolves your Query !!
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