1 x pci express x16 slot running at x4 pciex4 - AIIMS

Yes, you can plug into 16x slot, but off course it will run in 4x speed Some motherboard even let you plug 4x card into 1x

PCIe x16 slot with faster bandwidth and lower impedance 2 PCIe Slot PCIe x4 slot with Lower impedance

pcie 20 x1 slot Côté PCIe, nous avons un premier slot en x16 ainsi que deux en PCIe x4 et un dernier en PCIe x2 Côté Ethernet, nous avons

pcie 4 ssd in pcie 3 slot If you have the option of multiple slots where at least one supports PCIe, it's worth considering your secondary slot for an SSD upgrade When combined