I've got a Samsung galaxy s9+ with a broken screen. My idea was to use a hub like this 
to connect everything. My question is if I were to connect a powerbank to one of the usb c "outputs" would the hub draw power from it or would it try to charge it from the "master" device (ie. Smartphone)? And if it's the latter, would putting the powerbank on the "input" cable for the hub cause the smarphone to be unable to controll other connected devices? Edit: Also if somebody had done something like that before, any hubs you can suggest?
Charging with a powerbank should work depending on the dock but if you pick one where power is supplied via USB C you should be fine. Note that there are also dedicated Samsung Dex docks out there.