AD and RDS - what to throw into a virtual machine?

Question

Active Directory

Good day to all. I'm just starting to learn Windows Server, so there are stupid questions.
There is a German Dedik, quite powerful (16 threads, NVMe). 15-20 accountants will sit on it in 1C file mode and other software (with different enterprises, I will put restrictions on user access to folders). In general, the server needs mainly a file role, Hyper-V for several sites + a gateway, and RDS. AD is needed only for the latter to function and limit users, as a formality. There is no talk of any complex enterprise.

I have already decided that it is better not to combine some roles on one machine, so I will take either RDS or AD into a virtual machine. Hosting leases 2 Windows licenses - only for the host and 1 virtual machine in addition to it. It is impossible to rent licenses separately for each virtual machine, and renting Server Datacenter with its activation of child virtual machines is financially stressful. Therefore, something will have to be left on the host next to Hyper-V (I am aware of all the risks, I thought about the backup).

What is more expedient to throw in a virtualka - AD or RDS? I understand it is wiser not to allow users, along with the host (whether RDS on it), to take virtual machines with them, including AD, but there will be no external connections to the domain. Will user sessions work faster on a native machine than a virtual one (no matter how chic Hyper-V is)?

Plus, I can’t understand how disabled record caching (if you place AD ​​on a Hyper-V hypervisor) will affect the performance of virtual machines? Or is there a small loss on NVMe?