from the game manual playoff crunch is like a crunch time but the enthusiasm works like normal.while playoff normal is like a normal game but the enthusiasm works like a TIE game.
by default every team plays playoff crunch.so if there is an inactive team against you then u shall face playoff crunch.
the best strategy is to use playoff normal in those games which you are sure of winning and using playoff crunch in the tough games.
in the finals crunch the first game.if you win that game then use playoff normal for the second game to get a level up in enthu and then crunch the final game.
as far as let coach decide is concerned,it works in the same way as it does in the league games.so if you have used that before(and had good results,cuz let coach decide works for some and ruins the game for others) then you can use that.