Researching Bao-overnight proof

Researching bao for overnight proof. I made the recipe with instant yeast and baking powder. The yeast is still the primary leavening agent in the recipe (1.5 tsp yeast to 1 tsp baking powder).

My questions are:

a) is the baking powder going to toughen the dough overnight?

b) is the baking powder even necessary?

c) can I form them, proof them overnight, then steam them once? Or is a pre-steam/re-steam necessary?