My take which is not correct, but developing wrong idea really:
In cases where opponent is far from balanced play (25NL and under I would guess) 3bettin is just a tool to react against villain’s range and actions thus performing trivial exploitative play. This play includes 3betting with hands that have high relative hand value if called & blocker as a
bluff to have fold equirty or if you determine that villain will call 3bet with worse hands you can bet for value. Better you are, wider you can operate. Imo all is decided how good you play against opponent when he calls. Best player in the world you don’t mind if he calls when you 3bet AA, worst player in the 5NL pool you don’t care if he calls when you 3bet 8Js because you know you don’t lose that much against him. Now sometimes you want to end the hand as soon as possible because villain is too good for you, in this case you prefer to 3bet everything (mostly) you want to play for fold
equity and for to gain upper hand on post flop play if he calls, this range typically is quite tight though and for value mostly, but includes hands that if called you are not desperate.
EV value has a meaning, thus normally I have seen 55 to 65% equity value range suggested against his range. This is wrong in a sense that calling range of a villain is normally not decided by the range he opens in micros. Instead he either opens too much and folds nothing, or opens too much and folds almost everything except KK+. But typically if he opens normally or too little he folds way too much to 3bet and thus all advises (except blackrain ) are way off.
Ragequit has a good explanation as well as
Smokewood for different purposes of 3bet.