They mention keyboards with NKRO, but I have no idea what that means
You can safely ignore that in context of UHK.
As for normal typing, there should be no problem.
As to UHK’s fast input features (macro text action, composite shortcuts, modifier secondary roles), that depends on CharaChorder - it may or may not have problems. If there are problems, you may work around them by increasing UHK’s keystrokeDelay, or try to contact CharaChorder to fix the issues.
(The trouble is only that with some features, UHK sends keystate changes in quick successions, and some software does not expect it because a regular user with a regular keyboard just is not capable of that fast typing.)