PCIe Motherboard

Using LSI 2308 in PCIE x1 mode, what will I lose? pcie 3 slot But what about the fallback to PCIe , for example runs an older AMD or current Nvidia graphics card in such a slot? In order to remain really pcie 30 in 40 slot List of Motherboards with 3 PCI-Express x16 Slots: GIGABYTE B650 Gaming X AX V2, MSI X670E Gaming Plus WiFi, ASUS ROG Strix Z790-E Gaming WiFi II,

pcie 40 in pcie 30 slot The adapter card I am looking at can be used in a X4, X8 or X16 PCIe slot and they say I will get up to 32Gbps when it is plugged into a PCIe