Yes, you can install a 1x PCIe card into a 16x or 4x PCIe slot

Yes, you can install a 1x PCIe card into a 16x or 4x PCIe slot 4x pcie slot Should work fine, it's the same as putting a 16x card in to a slot that's only wired for 8x or 4x, you don't get the full bandwidth but it will 4x4 mega slot PCIe x1: These are the smallest PCIe slots, used for almost any other cards like average network adapters and USB expansion cards PCIe x4:

4x4 mega slot Hi Krusher_r, Thank you for posting in Wired Communities The network adapter is backward compatible to the PCI-E slot

4x4bet slot Difference between PCIe Gen 3 and PCIe Gen 4 With options for 1x, 2x, 4x, 8x, and 16x slot configurations, PCI Express doubles the speed Understand fully PCIe gen 4 Learn the main differences between PCI express and PCIe 3, specifications, applications, solutions & much