Okay, So I've been recently following SC Freiburg recently and Streich has been playing some beautiful football. Freiburg tend to use a 3-4-2-1 shape as base for all of their formations and so I could analyze their formations to be these two systems:
4-2-3-1: They do use this against teams that play with a back four and its been solid for them.
3-4-2-1: Preferred against back 3 systems.
I may be wrong but would love someone else try to replicate Streich and his philosophy.