Can You Use a PCIe Express Card In a Slot?

the PCIe slot There are essentially four types of PCIe slots differentiated by their lane Slot

The specs state that the PCIEX4 and PCI Express x1 slots conform to PCI Express standard In which PCIe slot did you drop the to PCIe x4

pcie x4 in x16 slot List of Motherboards with 3 PCI-Express x16 Slots: GIGABYTE B650 Gaming X AX V2, MSI X670E Gaming Plus WiFi, ASUS ROG Strix Z790-E Gaming WiFi II,

pciex1_1 slot 3 Slot x16 Gen4 PCI Express Backplane Dolphin's IBP-G4X16-3 three slot backplane enables customers to establish a remote access to two PCIe devices