There is nothing to worry about. You can always flash your stock kernel back, if any new kernel will not work, or will work unstable. Just try - and in any case you can always flash back to stock. That's that simple.C and H are the same one because they share Ericsson Thor M7450 modem. However only U uses Intel XMM7260. That's what I'm worry about.
ref. : http://forum.xda-developers.com/note-4/general/modem-hardware-versions-n910-list-t2926782