In order to seamlessly connect with MacBook Pro, there is no gap between adapter and MacBook Pro, remove the MacBook protective case before connecting the type C hub adapter.
Q3: Does this USB C hub fit if the MacBook Pro has a protective case on?
When they use at the same time, Thunderbolt 3 port can support max output, HDMI port can support max output.
Yes, they can mirror or extend the screen simultaneously.
Q2: Do the Thunderbolt 3 port and HDMI port can be used simultaneously for Video output?
If you use all ports at one time, for the stable connection, a PD charging adapter(sold separately) is recommended for power supply.