>>30568229your drop gets determined as soon as you start the stage.
it doesnt matter what stupid shit you do
no. you got the same chance with a SE team or only pikachu clones
no. buying items doesnt increase shit
no. it doesnt matter if you kill it off in 1 move or 20 moves
If the stage wants to give you a drop you get it. Doesnt matter what damage you deal at what point. Theory that you have to hit a special HP treshold to get a drop are proven wrong. I messed around with eevee and once got a big and two small cookie drops in 1 single hit (I basically went in all items with m-luke. And a 4match would instantly kill it off. yes supreme here) And I literally did hundreds of runs to see some pattern, but there is none. (If you wonder how this is possible. have cfw. backup your save. do the runs. re-import save. repeat)
Also there are some stages that have 50% for the 1st psb drop and some that have 25%. The first one is for shitmons in main stage repeats and often for the current competition support. The second one is everything decent, like machamp, emboar, bellossom, shaymin... And there is even a 12,5% for 1st psb drop for decent main stages like glalier or zoroark.
The game visualizes your drop at the 25%, 50% and 75% point of the HP. Your frist drop can happen at ANY of these. But you can also get a 2psb drop or sometimes even 3psb drop. Although this happens very rarely. For example the chance for a 2psb drop for a 25% mon is usually at 6,25%. And a tripple drop is at 1,56%.
tl;dr: once you start the stage, your drop is determined. there is no pattern. some stages have better drop rates, some worse. it doesnt matter what you do in the stage to "improve" your chances. Its all random and the drop happens around the set percentage
Something else important.
Emboars drop rate for 1psb is 25%. The chance for the 2psb drop is around 6%. And there is a small chance for a triple drop. And if we add up those we get around 30psb in 100 hearts.