What is PCI Express? Do PCIe lanes, slots, and versions matter?

Intel 13th Gen + ASRock Z690 Pro RS Build pcie 3 0 in 4 0 slot SuperSpeed Storage：3*PCIe Connectors; EZ-Latch：PCIe x16 Slot with Quick Release Design; Fast Networks：Wi-Fi 6 & GbE LAN; Extended pciex1 slot ​As mentioned above, plugging a x4 PCI Express board into an x8 slot is acceptable This setup is called up-plugging The opposite—plugging a x8 PCI Express

pcie slot dimensions Biostar ; 1, 1 x AMD Socket AM4 CPU ; 2, 4 x DIMM DDR4-4933+ ; 3, 4 x SATA III Connectors ; 4, 1 x PCIe x4 Slots ; 5, 1 x PCIe x4 Slots