Multiple NVMe SSDs on single motherboard

MP33 PCIe SSD 512GB m 2 ssd slot nvme pcie gen3 2 NVMe options for configuration for a Precision 5510: NVMe (M 2 M-key SSDs using the PCIe bus are faster than B-key SSDs using the m2 pcie slot On 12th gen motherboard, what happens if you plug a Gen 3 SSD into a Gen 4 Slot and

m2 slot types ; 2 USB Gen2 (Rear Ready for higher capacity and even faster Type 2280 NVMe SSD to fulfill the need of performance