Yeah, heard that performance should be no big deal, the nuc is perfectly suited for handling all current formats :). Unfortunately I don't know either, how to confirm whether the actual output is 10bit, but this would be the most interesting thing besides HD-Audio passthrough, which still seems to be not working if using HDMI connection and 4k resolutions, if I remember it correctly from forum.kodi.tv.
I have not yet tested the pass-through. I will be testing that this week through my AVR and I'll let you know. The first tests I did were direct to the TV, next I'll move it back and run it through my Onkyo in passthrough and let you know how it goes.