>The price difference is about $200 (not a small change). How important is for a VFP 9 application that the OS is Win 10 Professional?

Vfp does not care. For me main difference is RDP/MSTSC (remote desktop) support.
Friend of mine swears by Hyper-V as VirtHost, which is only included in professional, myself I want to free to choose OS ob physical HW, so I use Virtualbox, which can run under Home, Prof and Linux.

YMMV, esp in a tiny machine on those criteria ;-)