the cornstarch and baking powder add a little sweat protection/absorption but it’s mostly just a deodorant.
antiperspirants have active ingredients that chemically block your pores and sweat glands. they’re essentially topical pharmaceutical drugs. that’s one of the reasons some people refuse to use them. so as far as making your own antiperspirant, I wouldn’t try it.
if you want to give the homemade deodorant a try but are wanting to stay dry too, you can try a light dusting of cornstarch, baby powder or talcum powder anywhere you tend to sweat. I sometimes do that when it’s really hot out, on the small of my back or my crotchular area. it might leave white residue on your clothes, but if it’s underneath them it won’t be visible and it washes off easily.