[No Pepper]

I've read here and there that it is possible to edit the playoffs, but I need some clarification from those in the know (maybe I'm wrong altogether):

What exactly can I edit from default?

1) the structure as in #teams, which teams, #rounds?

and/or

2) the dates - who is home and away and when

When can I make these changes so it doesn't cause problems in the game?

Part of what I'd like to do is have 1 winner + 3 wildcards in a single division league, but I may understand that is not possible.

Thanks in advance!