What are the top uses of PCIe x1 Slots?

Today that PCIe controller will either be in the CPU or the chipset A bifurcation card handles power and control signal redistribution,

It means that the motherboard has 16 PCIe lanes and two connectors You can either use one connector and it will connect all sixteen

pcie slot sizes PCI-E x8 slot NVMe drives utilize the PCI Express interface to maximize flash memory potential and deliver the fastest SSD speeds available

pcie 4 ssd in pcie 3 slot Transfer speed: PCIe x16 to x8, 128Gbps Application: PCIe x16 graphics video card to PCIe x8 slot extension cable; Product description: ADT-Link