I assume you have already downloaded all the drivers from: Drivers & Software
I have found the Intel Driver Update Utility not the best at identifying later drivers, others have found the same and their is a thread in this forum just from the last couple of days on this.
For the 2.4GHz/5GHz, a couple of us have also found this issue as reported in this thread: NUC6i5SYH Wireless-AC 8260 not seeing the 5Ghz Band
I happened to be reinstalling Windows 10 for a different reason and found after the reinstall my NUC could then see my 5GHz network.
Probably makes sense to also post your details on the above mentioned thread.