Assuming that it is still +EV to stay at the table, which of the 2 adjustments is the best way to adapt against a 3b monkey?

open tighter, 4b bluff more.

If he opens tighter, should he not 4b more with value instead of bluffs?

He is exploiting the weakness of villain 3b range. Most 3b LAGs are going to continue often enough to put 4b bluffs in a difficult situation.

lol opening tighter is the worst "adjustment" you could make. You open the same range you normally do and call his 3bets a lot with anything that has playability. Basically never folding anything suited and only folding the junkiest offsuit stuff. You also slightly expand your 4bet range both as bluff and as value but only slightly don't go crazy.

3bet monkeys also have the tendency to auto cbet any flop even though they have a relatively weak range so you're going to want to check raise flops very aggressively. Basically don't be afraid to fight back. You'll get into high variance spots but that's the name of the game, tightening up means you're letting him win.

I’d like to hear others thoughts with 4 betting a merged range rather than a poled range under these circumstances?

I think 3 bet monkey is not sufficiently descriptive

Does he 3 bet kjo kto type of hands or 35s, 62s type of hands

If his 3 bets are very linear (he has no flatting range) I would think the correct adjustment is to tighten up and 4 bet more thin for value/denying equity

If his 3 bets are very polarized (he flats his medium strength hands) I would open the same range, not change my 4 bet range, postflop play will be more complicated against this range ..many different lines could be correct depending his postflop strategy..also you get to bet bet shove a lot more often when he does flat preflop )

I think 4 bet bluffing against an aggressive 3 bettor is a poor strategy generally because most aggro 3 bettors are likely aggro enough to start 5 bet shoving light for value or as bluffs. If you have stats that he plays weak tight facing 4 bets then it's an okay adjustment. But his high 3 bet % in and of itself doesn't mean he will overfold to your 4 bets.

Open a bit tighter, call the 3-bets a little wider, 4-bet more. Most of all, don't go on tilt and over adjust.

If he is 3-betting really wide like every other hand, you can begin 4-bet jamming Ax and pocket pairs while 4-betting smaller with JJ+ to induce a jam and be in great shape against a call.

This seems like an excellent post full of good advice. Thank you.