PCIe vs NVMe Compared: Related, but Not the Same!

2 standard contains variants with up to four PCIe lanes, one SATA 6 Gbs and or one USB port So it is possible to connect PCIe as well as SATA SSDs

You'll be able to do more with less in this case, since a PCIe x8 slot can handle almost exactly what a PCIe x16 slot can currently

m2 expansion slot You can have one, four, eight or sixteen lanes in a single PCIe slot, denoted as x1, x4, x8, or x16 PCIe technology enables interface speeds of

m2_1 slot PCI Express ; Dual simplex, up to 242 GBs · Serial · Yes · Yes · pcisig