Basically the question Should I correct an imam who forces his opinions on his community? is the reason for me to ask the above question.
As I know (or learnt) that even if abu Hanifa holds the opinion that in a congregation the people following the Imam can end the prayer at the same time with him or earlier, but Mohammad ibn al-Hassan a-Shaybani and abu Yusuf followed the opinion of the majority of scholars saying one must follow the Imam and only do the salam if he has finished it.
So I asked myself what is the established madhhab of the hanafi school and whom are the scholars whom made this final stablization.
BTW it would be nice to know the same for the maliki and hanbali (and if possible also the dhahiri/zahiri) school as i assume that i've covered the shafi'i school already in my answer on Levels of obligatoriness of rulings within schools of law