A:Answer I used Crucial's parts selector (enter model info, find parts) to get 64GB with 4 sticks, the motherboard is bit finicky about timings (and has no real BIOS tuning to speak of for it) so "just any old sticks" or "super fast sticks" seem to be cause problems for people. Mobo capacity is capped at 3200 MHZ, and 64GB, ("Supports up to PC4-25600 (DDR4-3200)")
I used Crucial Ballistix 3200 MHz CL16 BL2K16G32C16U4B, since it didn't make much sense for me to pay for Mhz I couldn't use, and the RGB support (even with the included sticks) wasn't working right out of the box, so a plain black heat spreader was fine by me.