I'm doing a Tower 900 build "White Witch" and am trying to figure all of this out. I did the plus fittings, pumps, etc. and the few hairs I have left are in severe peril. I do feel your pain my friend. I hope I don't have to go the same route... I hope your build goes better, as the case has so much potential..
I have the pacific pr-22 d5 pump rgb plus x 2 and they require a 2.0 header per pump as best as I can tell from the volumes of instruction (I jest of course). I'm going to go with one of these www.amazon.com/NZXT-Internal-Controller-Black-AC-IUSBH-M1/dp/B01IFGFTJ2 so I can do the pumps and still use the header for the front panel. I have an MSI Z390 Godlike mobo and it is amazingly short of USB headers as well. One would think for over 5 bills one would have more than they can possibly use. I think the type c port on the box (if it's a plus) is for linking two boxes per the instructions