Can I plug a USB into a thunderbolt port?

thunderbolt card in another PCIe slot than the only slot that's designated for it Even on supported

thunderbolt card in another PCIe slot than the only slot that's designated for it Even on supported

thunderbolt slot png Thunderbolt 3 PCIe expansion chassis with 60W power delivery for two half-length PCIe cards

guru slot Full line of single and multi-slot Thunderbolt PCIe Card Expansion Systems to add PCIe cards to Mac and Windows computers