Can You Use a PCIe Express Card In a Slot?

I recently got an LSI 2308, and have not had a chance to test it yet My motherboard only has one PCIE x16 slot ,

For example, if you connect a PCIe expansion card to a PCIe slot, the card will perform to the PCIe specs PCIe Gen 4 offers

pcie 50 slot PCIe slot you plan to slot it in Below are the speeds of potential M Expansion Card - 3 SIIG SC-M20014-S1

pcie 30 x1 slot First of all, I know that a PCIe 4 SSD NVMe will be running at gen 3 speeds and bottlenecked by the PCIe 3 slot But I'm wondering if there are