Alright guys - thanks for all the suggestions, hints and infos!!
Here is my (rather late) reply to hook you up with the results - and the intention to help other people who will face a similar challange, of course.
In the CL-final, i made a minor change to your suggestions and went for a 3n-1-3w-1-2
As Master Tactician said, if anything i wanted to try n exploit his wide defense, as well as the fact that he's playing without a DMC. This left him some room in the midfield, but as my DMC had a red arrow, it seemed like my players were able to balance his majority...
Having said this, you might already guess that this one went pretty good for me: My team won 4:0 with him not having a slight chance: I had more ball posession, more shots on target, more passes found their receivers...
More than that, i feel that the choosen tactics were the key to success: Defensive mentality, whole pitch pressure, attacking through the middle, mixed passing, no OT, no Counter.
@Master Tactician: Again, thx a bunch for the hint, mate. I would indeed never have used defensive mentality and whole pitch pressure, but it apparently worked like gangbusters
The other final - the CUP - i unfortunately lost 1:2...
Here's how it went: I chose to play 4-1-4-1 with red arrows on the wingers, own half pressure, attacking through the flanks, normal mentality...
First thing i got to read after kick-off was something like "XY tries it from the distance - BOOM", goal in t second minute...
Apart from switching to offensive mentality instantly, and to whole pitch pressure at around minute 30, i decided to not change formations in the first half...
After he scored the two-nil lead right before half-time, however, i switched to 3-5-2 V-Style... the game went on, the statistics didnt seem to change much, and my team managed to at least score one goal right before the final whistle...
Dunno if it really was about the tactics or just bad luck with the game engine though... again, i had more posession etc. ...
Anyways - going again for the treble this season.
Good luck, Best
tl;dr
Against 3w-4-1-2 (note that the opponent was like 8 points stronger than me):
3n-1-3w-1-2 worked fine!!
Defensive mentality, whole pitch pressure, mixed passing, through the middle - afair i put blue arrows on two of my DCs...
Won 4-0
Against 4-1-3n-1-1 (opponent was about the same strenght):
4-1-4-1 (first half) didnt do too well - I was down 0:2 at half-time.
However: i started off with normal mentality, own half pressure, mixed passing, through the wings, red arrows on the wingers...
3-5-2 V (second half) went better - My team managed to score at least one goal, whilst his didn't score another one.
I set the tactics to offensive mentality, whole pitch pressure, long passing, wings (of course), and removed the arrows from the wingers that were then playing as AML/AMR.
Lost 1-2