What is a PCIe network card?

That will work for old cards, but it can't go back to PCIe The riser slot on the motherboard x32? so I tried to Google around From

PCIe cards can always operate in PCIe slots with the same or more lanes than the card For example, an x8 card can operate in a slot with x8, x16, or x32 lanes

pcie slot size x32), 1 Gen Z 4+ ; 6 SlimSAS ; Supports 1 M PCIe Expansion Slots PCIe x 32, 1 Gen Z 8C

pcie 4 card in pcie 3 slot The PCI Express slot commonly used for graphics cards is typically an x16 slot, which is one of the fastest connections on a motherboard