2 slot. SATA-based M.2 SSDs are all well and good, but mostly restricted to economy models these days—PCI Express is where the cutting-edge speed is. Your system specifically needs an M.
Today's mainstream solid-state drives are PCI Express 3.0 and 4.0 x4 NVMe M.2 devices, and they leave the fastest SATA-based drives in the dust. (Credit: Zlata Ivleva) ...