Using 4 Stick Memory better use Asus Maximus with 4 DIMM, because it using T-Topology all slot can clocking almost same, 4 DIMM board that not using that topology will have hard time to boot.
On Z270 Apex it will mazed around 4080-4140 32m waza on air, on X299 Apex with Kaby Lake X you will have more if not limited by memory. This all at C12 Tight