So the manual for the Blackbird doesn't have much to say about the memory, besides:
DDR4 1600/1866/2133/2400/2666 ECC
The wiki says more:
must be registered (RDIMM); must NOT be LRDIMM.
The supported memory speeds are 1600, 1866, 2133, 2400, 2666 MHz.
Ram will be running at a potentially slower frequency (2666, 2400, or 2133) based on if there is 1, 2 or 4 DIMMs per channel
So as a noob to this stuff, what is a good approach to picking RAM for the Blackbird? For example, would 2 8GB sticks be better than a single 16GB? Or is it better to leave a slot open for a future upgrade? How much does the speed matter?