I need to get a hub that connects to Thunderbolt/USB-C on my Mac. The hubs I see have USB-3 ports, an Ethernet port (which is all nice) and a "USB-C Power Port". My question is whether that USB-C power port is JUST for power, or can it be used as a regular USB-C port for data transfer? I would very much like the latter, because once I plug this thing into my computer USB-C port, I have one less USB-C port on my computer to use for other stuff. The latest iMacs have only two Thunderbolt/USB-C ports, so such ports are kind of precious.