Ssd sata and ssd nvme pcie slot compatibility

PCIe Carrier board is one-slot-wide, half-height and it compliant with PCIe Specification and Specification PCIe Carrier Board supports x4 PCIe Gen

First of all, I know that a PCIe 4 SSD NVMe will be running at gen 3 speeds and bottlenecked by the PCIe 3 slot But I'm wondering if there are

m2 slot screw 2 slot switches the GPU slot slot to 8x gen 5 But there aren't gen 5 lanes only, and 20 gen 4 lanes For a motherboard to support

m2 expansion slot m 2 gen 4 in gen 3 slot NVMe SSDs that support the newest Gen 4 2 slot but cannot find any information about its supporting PCIe generation (4