TB3 uses the USB-C connector and allows extra things like power delivery, Displayport pass through as well as higher total throughput (40Gbps from memory). With a simple USB-C to DisplayPort or HDMI adapter you run your monitor directly off your internal video "card".

The DisplayLink stuff is a self contained video "card" that connects via USB. So in theory you can have many of them connected. I think I've seen a demo with ~16 connected at once.

USB3 is just USB (so no video passthrough or power delivery). So any display connected via a USB3 only port will require DisplayLink or similar adapter.

USB3 can be supplied via a USB-C physical interface so you can't tell by looking at the port.