I played nearly a full season and tested different variations. I didn't achieve satisfactory results with the planned 41212 narrow diamond formation and the flow of the game wasn't what I wanted either. The playmaker in AMC was usually too far foward and often covered, so he wasn't integrated into the passing game as I wanted. Defensively, there were too many gaps in central midfield or on the wings, depending on movements of the two central midfielders.
Therefore I pulled back the playmaker into central midfield and set him on attack. With this "simple" change, it's much better both defensively + offensively and there are good passing situations and player movements.
Current formation and roles: GKd - WBs CDd CDd WBa - DMd - BBMs APa CARs - AFa DLFs
Mentality: balanced
In Possession: shorter passing, higher tempo, focus play through the middle
In Transition: counter, distribute quickly, distribute to center-backs
Out of Possession: mid block, higher defensive line, drop off more, trap inside