PCIe NVMe SSD on PCIe slot-Worth it?

Eight NVMe SSD slots on a PCIe x16 card Silent operation Add your own ultra-fast SSDs for Mac, Windows, and Linux

It looks like there are different PCIe specs Dell's slot can be used for Intel Optane memory or for a bootable SSD apparently PCIe now

nvme m2 slot when looking at NVMe SSDs With the previous generation, the maximum bandwidth available on an slot with its four PCIe lanes was 4GB

nvme m2 slot motherboard In this video, I tested the PCIe gen 3 slots to see if there is any performance difference when