It has two DDR5 SO-DIMM slots up to 64GB, two M.2 2280 slots, and two drive interfaces supporting M.2 NVMe PCIe 3.0/4.0 SSDs. It does not support SATA SSDs. Each drive interface supports a maximum of 2TB, and the entire system supports a maximum of 4TB.
I've purchased from them multiple times. Once, my computer was damaged during shipping, but they replaced it for me.