You can then connect many different types of Thunderbolt and USB-C devices to the three Thunderbolt/USB-C ports on the back of the dock.  The type of functionality provided by the two ports on the back of the dock is ultimately determined by the capabilities of the host computer.

To put that another way, if the host computer has Thunderbolt 4 technology built-in, then both ports on the back of the dock will function as Thunderbolt 4 ports.  

If the host computer has Thunderbolt 3 technology built-in, then both ports on the back of the dock will function as Thunderbolt 3 ports.

If the host computer has USB-C technology built-in, then both ports on the back of the dock will function as USB-C ports.