The Teller Ullam design with data India has. The megaron design was not used because it cannot be tested in Pokhran and also in todays world the need for megaton devices is questionable
No one will like to continue megaton devices. The area of destruction covered by a MIRVED submegation devices is larger. That is why people have moved away from the Tsar Bomba type of devices or else they would have continued with those.