Wanted recommendation : pcie to card

After a quick Google search, I found this article which explains that: a PCIe x16 slot can theoretically hit approximately 32 gigabytes

A PCIe graphics card in a PCIe slot will be limited to PCIe speeds The Number of PCIe Lanes Is Just as Important as the Version

pcie 20 x16 slot PCI Express Gen 3 x8 but i get the same behaviour if i put it in slot 4 (PCI Express Gen 3 x16 ) is this a known issue

pcie 3 slot It provides PCIe slots 1 to 3 when installed in IO module 1 and PCIe slots 4 to 6 when installed in IO module 2 Figure 2-32 3 x8 riser cards