If you buy an Intel NUC, I think I'm right in saying that they are all licensed for Windows 10 (but perhaps others know better!). Mine came with Win 10 pre installed.
You dont need the other items, I control mine either remotely from another machine using VNC (a free remote access program), my Android tablet (with Gizmo or Eos) and a cheap second hand Logitech Harmony One remote controller. For the last option, I do have a screen attached. I never intended to use it that way, I originally thought I'd use it "headless" for audio only, but as soon as you realise what JRiver can do, ie add TV, video and photo viewing as well as superb music playback it just seemed a no brainer to add a screen.
On the odd occasion I want to update the bios or similar, I just plug in a dongle from a Logitech wireless keyboard from my desktop. I can particularly recommend the Logitech remote as I have it configured to switch on the NUC, screen, DAC, and amplifier with one button press and off is also one button. And it works brilliantly with the theatre view in JRiver. TV is supplied by an HDHomerun tv server, another neat solution.
So many options, and its very satisfying to get it all working!