A:Answer I upgraded mine with a 1TB M.2 NVME SSD, 1TB was the max that was listed for the second drive, but that might not be the true limit. It also supports SATA, probably either HDD or SSD, but only one of them was listed as officially being supported. IT DOES NOT come with the standoff needed for an m.2, though, so you'll need to purchase some (I got M2.O*2.5mm standoffs/screws).
The RAM is also upgrade-able, with only one slot being used as it ships. I upped mine to 16gb, but more is theoretically compatible.