NVME M2 drives: which slot to use?

In this video I discuss the difference between an SSD and a NVME PCI-Ex4 SSD From how

2 drives are “keyed” at one end so as to prevent the end-user from inserting them in an incompatible socket PCIe NVMe drives are 'M' keyed SATA ones,

nvme in pcie slot The WD_BLACK SN850X NVMe SSD 1TB and 2TB drives have an optional heatsink 2280 Connector Compatibility Windows® 11, 10, ; PlayStation® 5

nvme gen 4 in gen 3 slot When you buy an SSD like the Crucial T500, you may see something like 2280 in the title, which is a combination of its dimensions — 22mm and 80mm in