Hello Ethan,
They both can be used for your examples and have virtually the same meaning:
Shallow - showing a lack of depth in thinking
Superficial - perceiving things at a surface level, ie. without depth.
Note: a LACK of depth and WITHOUT depth.
When discussing a way a person views something (their action), you would use Superficial, and if you are describing the person themselves, you would say either Shallow or Superficial.
Hope that helps