Yeah, you were right about the CMs/DMs. Moving them up or down the field adds a complexity layer that, although can be manageable, can make things more complicated. Sometimes we have players that do well both positions, but sometimes we don´t. I also felt that the 4-2-3-1 was too risky and the 4-4-1-1 was not being good enough on counter attacks. In fact, the 4-4-1-1 is a complicated formation because it lacks a lot of power on the flanks on the last third.
So I thought that, if I really want to change the strategies and become more flexible, I should stick with the same formation. Then I decided to go with a 4-4-2: simple, easy and very flexible.
I used some tactics from Rashidi´s YouTube channel as templates for the more attacking formation, which is this one...
...and for the counter 4-4-2, which is the one below.
For the most defensive strategy - used on games against very hard opponents and to hold on comfortable leads/end of matches - I decided to give it a chance to FM´s 4-4-2 Park the Bus template. I saw a video on YouTube in which the tactic worked very well and I thought that on some circumstances it could be useful.
The first tests with this system went very well, including good matches using Park the Bus when necessary, but then I decided to stop playing FM. I came back recently with a new save and I have been playing pre-season, now using this system from the very starting point.
Despite the tactics itself, I think that being flexible is key here. If we always adapt our strategy we have much more winning chances than trying to insist on playing always the same way.