wing loading should be the area of both wings added together....but I am no math wizard
No you won't see a greater loss of altitude in a bank with a bipe.....Bipes are made to knief edge....there is a greater amount of drag with a bipe....all the support for the upper wing....so you might need a bit more power on approach.....
the two wing types...either will fly inverted.....CG will have a greater effect on inverted flight than wing type....the further aft the CG the less "push" you will need on the elevator to maintain level flight....