INS 503, baking powder, and baking soda have a similar chemical composition. Ammonium bicarbonate or e503ii is a chemical compound that can be used for cooking various types of bread. Baking powder is also another alternative to it with a kind of similar composition.
Baking soda refers to Sodium Bicarbonate, which has a distinct chemical composition. Although baking soda gets utilized for baking, it is less reliable as compared to the other two. If you need a mild raising agent like for cookies or cupcakes, then baking soda would be enough.
But to create a full-fledged cake or bread buns, baking powder or INS 503 is a far better option. But excessive use of baking soda can also lead to some health issues.