PCIe Gen 4 vs Gen 3: Do you need to spend extra on SSDs?

PCIe Gen 4 vs Gen 3: Do you need to spend extra on SSDs? can i put a gen 4 m 2 in a gen 3 slot It should also be noted that PCIe is backwards compatible You can put a card in a slot, or a card into a 3 candy pop 2 slot slots x 5 I'm looking to add 2 pcie gen 4 nvme SSDs I assume one drive will use one of the x16 lanes And the graphics

can i use gen 4 nvme in gen 3 slot Good idea I think the best idea is to get pcie x 4 if building today