I always thought Merged and Depolarized were the same thing. In any case, you want to be 3betting people who call a lot with a wide range of value hands - if they call 3bets with 99, then you can 3bet with TT for value, or KJ etc.
If they fold a lot to 3bets, you want to be 3betting them with a polarized range of nut hands and junk - so you can still 3bet AA/KK for value for example, but you really don't want to 3bet say JJ against them, because they will fold a lot and you'll get no value for your pretty strong hand, and because when they do call you'll be way behind their tight calling range. However, you can 3bet them with 57o because they fold a ton - when you're called, it's easy to shut down and be done with the hand, wheras if they called you and you held JJ and had an overpair, it's easy to end up putting more money in the pot when you're behind. If they have a tight calling range, you are mostly 3betting them with junk as a bluff, but when they do call and you continue the hand beyond the flop, you show up with the nuts more often than the 2nd best "good" hand.