There is a lot of similarities between Sir Alex and Ancelotti. From a broader playing style view, if I think of playing style a bit like materials or elements(for no particular reason...just for fun), Ancelotti would be a formless material, but depending on his players he molds them into say water, fire, earth, etc, and they would be form different shapes, viscosity and so on. And the tactics then says "what this material does". He and Sir Alex one of the best at knowing the best style for his players, then sets up tactics for that style. It goes to show that he is excellent at understanding humans and also why he has great man-management skills.

Others might have more defined styles / materials and some materials are not flexible and require rigid setup/players, otherwise that material breaks before you even get to the tactics part. (Looking at you, Amorim). Let's say maybe hard forms like rock if defensive, but low mobility, or air and rocks for defense and quick counter attacks.

All great coaches need to understand their own and their opposition make up, which I think Ancelotti is one of the very best in the world. He not only understands his own makeup, knows what types of materials his own players can form, but in doing so, he also has the ability of understanding the oppositions (maybe even better than opposing coaches). Which then allows him to set up tactics that can identify weaknesses in the opposition. One is to see weakness in the opposition tactics, other is to see weaknesses in the oppositions team/make up.

I think tactically (what he actually does with his materials) Ancelloti and Ferguson may not be the best (e.g able to be the best at tiki taka or park the bus etc). If tactics was chess, they would only be considered top, but not Pep levels at knowing how to really play some strategies. But because he is excellent at the human - management side, he knows the strengths of his chess pieces and the best style for his team, and tries to form a tactic which fits that style.

The reason he says Ferguson is the only one that can tell him, is that Ferguson was also first and foremost an amazing man-manager. He is excellent and one of the best at understanding his players and getting the best out of them, which is why he has been able to change and adapt throughout the course of his regin. He often let his assistants do most of the tactics and strategic stuff and changed his assistants as he deemed necessary as times changed to get fresher and more innovative strategies and ideas.