linux - Network Interface Card not using the correct PCI link ...
Yes, you can use a Pcie 3.0 graphics card with a Pcie 4.0 slot. Even though Pcie 3.0 and Pcie 4.0 have different data transfer rates, they are cross-compatible.
10 Things That Can Be Plugged in PCIe Slots - PC Guide 101
It is important to note that PCIe slots are not backwards-compatible, meaning that a PCIe x16 device cannot be used in a PCIe x1 slot, for example.
What GPU can my motherboard support?: how to check GPU and motherboard ...
Can I Install a PCIe 3.0 Compatible GPU on a PCIe 2.0 Slot?