So I was thinking, if villain overcalls a preflop 3-bet we can underbluff as an exploit.

But what if villain overcalls the preflop 3-bet, but he then overfolds to a flop c-bet.

Assuming he won't adjust to an exploit, could we then just calculate the EV of each exploit and choose the highest one. So the EV of underbluffing preflop 3-bets vs. the EV of playing balanced preflop 3-bets and range betting flop. Whichever is highest EV we then choose?

And to take it one step further, could we actually overbluff PREFLOP (despite the fact that he is overcalling) to further exploit the flop overfold? Or am I missing something here? Ofcourse, if he folds range on flop this would make sense. But if he calls occasionally, would we lose EV from all the extra check give ups on the turn?

Obviously it depends on the extent of each leak

Yeah this is what I was thinking. But what about what I said here:

"And to take it one step further, could we actually overbluff PREFLOP (despite the fact that he is overcalling) to further exploit the flop overfold? Or am I missing something here? Ofcourse, if he folds range on flop this would make sense. But if he calls occasionally, would we lose EV from all the extra check give ups on the turn?"

Again, it depends on the specific numbers

Larger pots = larger mistakes. Overfolding flop is a bigger mistake and would "count more" towards your exploitative decision.

You'd still have to weigh the probability of each mistake though. And you can add infinite levels of complexity on top of this. Don't go too far down the rabbit hole!