Good article. I converted my remaining Windows to VM a couple of years ago and struggled with trying to attach a physical Windows drive to VM. A couple notes:
If you do not have an activation key, the PC key is probably hardware embedded. Install the package acpica-tools on a Linux running the machine.
Run "sudo acpidump -n MSDM"
At the end of this dump is the Windows activation key. This machine key can be used to activate your VM. Just type it in like a purchased key. Do not use it for other machines, one per customer.
Always shut down Windows properly before attaching the drive to Linux to avoid the NTFS disk problem.
You are so right about performance. Win 10 did not scale well for me. It liked getting more memory and CPU, but it would barely run on previous allocations after playing with increased RAM and CPU. Finally I just reinstalled a fresh copy of Win 10 as a VM and installed my one app. You can create a Samba share on your Linux that any Win box (VM or physical) can access as a mapped drive on the same network. Lots of help on that out there. Just remember to set both the share permissions and the file permissions so WIn can use it.