Take a look at http://windows.microsoft.com/en-us/windows-8/multitouch-hardware-reqs.
For example, touchscreens that support fewer than five simultaneous touch points don't work with certain features and apps that are part of Windows 8 and Windows 8.1.
Windows requires five touch points it self so certified hardware should be good to go, you'll have to look up the touch specifications of the hardware itself.