1. It depends.
2. It depends.
3. It depends.

Wing loading depends on the size of model, the expected payload and what the expected power on/off ratio is.
Airfoil depends on expected airspeed, that is, how long you expect to be flying for.
Balance will depend on whether you intend to fly from the ground, or whether you expect the thing to be a bit autonomous.
Altitude will depend on the answers to (1) and (3).
Evan, WB #12.