How will a PCIe Gen x 4 SSD perform in a PCIe slot?

Sonnet 8x4 Silent Gen4 PCIe Card m2 pcie 4 0 in 3 0 slot With this NVMe SSD PCI-E X1X4 Adapter, you could add a NVME SSD on your motherboard without slot m2_1 slot 4 * NGFF Key-M NVMe Slot To PCI Express PCl-E 16X PCIe X16 SSD Converter Adapter Raid Card 32Gbps, You can get more details about 4 * NGFF

m2 slot mainboard Just to be clear, you can run a PCIe SSD in a PCIe slot , it just runs at PCIe speeds Which kind of negates the purpose