To put this into perspective - and we're talking idle drain here - the difference between "Doze on/Always On off" and "Always On on/Doze off" probably works out to a difference of 1% total an hour. Doze will bring idle load to 0.5% an hour or less, and people say A-O is 1 to 1.5%.
Now, for the most part, with general usage (not trying to dominate in Asphalt 8), I suspect the S7/Edge will be in the low/mid teens for active, screen on battery loads... 13% per hour... give or take.
So in that context, over the course of a day, Always On might cost you one to two hours of screen time.... depending on how much you log on the thing.