PCIe X1 to X16 Slot Extension Adapter Add-on Cards & Peripherals

Yes, a x1 card should work in a x16 slot It's good that you've got it to work in a x1 slot What else have you tried it in besides the x16 slot

Physically yes, the slot connector for an x4 is generally smaller and PCIe is designed that smaller cards can occupy larger slots if needed

pcie slot cover Yes, a x1 card should work in a x16 slot It's good that you've got it to work in a x1 slot What else have you tried it in besides the x16 slot

pcie slot splitter AMD B550 Ultra Durable Motherboard with Digital VRM Solution, PCIe x16 Slot PCIe x16 slot with faster bandwidth and lower impedance 2 PCIe