How to determine from command line if NVMe slot is gen 3 or gen 4?

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

3 Best 2TB+; 4 Best for Steam Deck; 5 Best for PS5; 6 Best PCIe 5; 7 How to spot the best deals

can you put a pcie x1 in a x16 slot Does anyone know if you can buy a PCIe x16 low profile card that supports FOUR M2 NVMe drives A pcie 3 x16 slot modded to 4x

candy stash slot You don't need PCIe support to run Nvidia's RTX 3000 series or AMD's Radeon RX 6000 range, and the performance increase isn't as noticeable