Recently I found quite surprising evaluations for me, especially in KNPP vs. KB, where the defending side could hold a draw just with waiting moves, not winning one of the pawns immediately. The h+f pawns with bishop holding promotion square is probably one of those theoretically most important and straightforward draws, but I saw many with pawns being on different files with one file gap and even pawns many files away like c+g.
I just wonder if there was some research on this topic and if there could be some rule said when position is drawn and when it is lost, in both KNP vs. (K)B and KNPP vs. KB. It looks like the bishop can stop some pawns almost forever, giving the king enough time to go sightseeing, grab a very distant pawn and return with very little stress to achieve a draw.