Will a GTX 960 run in a 1xPCIe x16 Expansion Slot?

The use of expansion slots was begun when the development of first computer started At that time, there were no built-in ports available

Now for the question, I see lots of back panel USB cards for PCIe slots But can you plug that card into a PCI-Ex16 slot AND have it work?

pciex4 slot No, I don't believe it is It looks to me like pcpartpicker has assigned the Gigabyte wifi card to PCIe first, taking the top x16 slot; and then it doesn't know

pcie x1 slot function Thunderbolt 3 Host Connection · 1 x PCIe x16 Expansion Slot · Supports Full-Size, Double Wide GPU · 650W Power Supply