So build the desktop, stick it in your attic, attach e.g.
http://www.wootware.co.za/asus-usb-ac53-wireless-ac1200-usb-adapter.html or
http://www.wootware.co.za/asus-usb-ac56-wireless-ac1200-usb-adapter.html or run a LAN cable through the roof, use something like
http://www.wootware.co.za/intel-stk...-storage-windows-10-32-bit-compute-stick.html and plug it into the screen, though you'll be limited to one screen, which you'll most likely hate.

(though you can try
http://www.wootware.co.za/j5create-jua350-usb-3-0-hdmi-display-adapter.html for two screens as the compute stick has a USB 3.0 port. Windows 10 should support multiple desktops if it is not the home version, not sure with that stick. Else just look for another program that support it. EDIT:
https://www.youtube.com/watch?v=pYUdAWOGJ_Y interesting.)
802.11ac I get 1ms or less latency as long as I am less than two walls away.
Just saying the above as an alternative as you don't seem to be able to make up your mind.