People usually say the 4betting IP should be more polarized and OOP should be mixed.

I always had a hard time 4betting OOP, since I usually don't know what kind of hands to pick as a "bluff", and if I should 4bet all the AA/KK etc hands, since it caps my range.

When people say 4betting OOP should be mixed, they are referring to the overall range? Like, 4betting half AA/KK/AKs and also some other hands (mostly hands that are also profitable calls and not hands I would otherwise fold) or 4betting all the AA/KK and than add those mixes?

I used to 4bet UTG vs BTN, for example, mainly with AA/KK/A5-A4s and some % of AKs versus some guys, but I usually read this is wrong. What a decent range do you suggest in this situation? Thanks!

4betting is really linear in general. You'd only want to polarize if people aren't really flatting your 4bs

Thanks for taking the time to help!

So, is something like AA/KK, half AKs and 25% AQo, for example, EP vs BTN a decent 4betting range?
Do you think that capping my range is a problem here? (some people, like Peter Clarke, advocate no 4bets in these spots)

You'd want to start with what the BTN is 3betting with and how he reacts to your 4bet.

To some extent the 4-bet range should always have some degree of polarity, because you 4-bet the top of your range for value, you call with the middle of your range, and you 4-bet some bluffs. (You fold even worse hands).

When you're OOP facing a 3-bet, not many hands can profitably call, because it's so hard to realize equity when you're OOP vs the player that has the range advantage. (He has AA/KK/AK in his 3-bet range, but hands that have decent equity vs those nut hands don't play well with low SPRs OOP. e.g. 65s has a lot of equity vs AA, but it won't realize that equity OOP, so it has to fold). Ergo, the hands you flat OOP will be those that realize most of their equity on the flop, because they make strong sets, top pairs or nut draws. Examples would be TT/99, AQs, AJs.
Your 4-betting range is usually comprised of value hands that can play for stacks (QQ+), and then some "bluffs" that have blockers to villain's 5-bets, but that also won't make (as much) money as calls.
e.g. In UTG vs a BTN 3-bet, you might 4-bet QQ+ and happily stack off, and you'll balance with something like AK, KQs, A5s, A4s, as these combos block villain's 5-bets but also play reasonably well if he flats your 4-bet (with stuff like ATs or JJ/TT).

When you're in position facing a 3-bet, such as BTN vs SB, you can flat with a much wider range, because hands like A5s, 65s, T8s, or QJs can realize their equity in position. In that situation, you might 4-bet and stack off JJ+/AK ("for value"), but this time your 4-bet bluffs will be lower ranked hands than before, because you have so many "mid-range" hands that can call the 3-bet. e.g. When it was UTG v BTN, you can't call with ATs or A5s or KQs OOP, so you 4-bet them. When it's BTN vs a SB 3-bet, you can call with all those hands, and your bluffs would instead include things like ATo, A6o, A5o, A4o, which won't make money as calls even in position, but do at least have blockers to villain's 5-bet range.

Thanks for the reply.

I actually agree with almost everything you said.
That's how I play BTN vs SB for the most part.
And I actually agree that some KQs might be even better than Axs as a 4bet utg vs btn 3bet, since it blocks AK, KK, QQ, AQs, unblocking the Axs bluffs.

I don't agree with 4betting QQ there (at least not always). I don't think it would be in a great shape on avg if we gii (particularly in micro and small stakes).
And I think calling with 65s to the 3bet (altough it is tough to realize our equity) is a good play. I think it is preferable to call with some low suited connectors then some broadways that are often dominated. And since people are using smaller 3b sizings IP, we still have to defend a decent chunck of our opening range there, and we got to find some hands.

You've said this a few times, but I am not sure what you mean by capping your range. If you are 4-betting your nutted hands your range isn't capped. Do you mean if you flat here your range is capped?

Exactly, it caps my calling range!

You could mix in a small portion of AA into the calling range.

The truth is I struggle with this same problem OP. I have been considering creating a 4-bet/fold strategy and see how it plays out. I will let you know if I get around to doing it and how it works. This is one of my weakest spots as well.

Don't flat AA, just 4-bet and be prepared to get it in. You can protect your range better if you flat it, but I think you'll make more money just getting it in. The more you 4-bet AA the more you can 4-bet bluff too.

I believe it is reasonable to slow down with KK sometimes. I'm usually 4-betting it versus most people in most positions, but lets say we open UTG and the BB 3-bets. I'm probably just going to flat, because BB 3-bets are going to be a lot stronger.

4-betting a button 3-bet with KK+, AKs, A5s, and A4s is really good. Not sure where you read it is wrong, but I think it works great. Maybe drop the suited aces versus some people. You might even be able to slip KK into your flatting range if we are talking about full ring or a really really tight player.

I think it is reasonable to call 4-bets with AA, but even then I like getting it in most of the time.