How much performance loss will I do if I use a PCIE 4 supported

PCIe boards can fit into slots designed for their lane configuration or higher Plugging a x4 PCIe into a x16 slot is acceptable

PCIe uses four lanes for storage devices 2 slots where at least one supports PCIe, it's worth considering your secondary slot for an SSD upgrade

pcie 30 x1 slot PCIe uses four lanes for storage devices 2 slots where at least one supports PCIe, it's worth considering your secondary slot for an SSD upgrade

pcie 3 slot Card and slot types exist for x1, x4, x8, and x16 links Matrox A x1 electrical card in any compliant PCIe slot will always run in x1 electrical mode