Preflop bluffing hands included in 4-betting ranges tend to vary based on positions, but even then I've seen a lot of different 4-betting ranges being used in different places (e.g. GTOw, instructional videos on sites like Run it Once, etc.)

What kinds of hands do you like to use as 4-bet bluffs in in different spots? What's your rational behind using them?

Rule of thumb is if you're OOP, go more linear (KQs, JJ/TT). IP will defend by mostly calling, so you need good equity when called. Of course it sucks to face a jam with KQs, but it's not something that should happen very often.

IP you want to polarize more (Q9s, ATo) because OOP will tend towards playing 4b or fold. So equity/playability isn't that important, and instead we try to avoid 4betting hands that suffer facing a jam.

Thanks, this is a good start

You can't go too wrong 4-betting Ax suited wheel cards, AQo and AJo. Obviously you don't want to do it at full frequency, but these are pretty solid. They all block AA by 50% which is super important. AQs and AJs are usually strong enough to call a 3-bet, so AQo and AJo are good for 4-betting as a bluff which blocks some premiums. Stacks will be shallow if you get called so when you hit an ace you can stack off more often. This assumes 100BBs of course. At greater stack depths you do have to include more hands for board coverage, but I'm not so good deep stacked. Suited wheel cards can sometimes hit the straight or have good barreling opportunities. A5s in particular has the best naked equity against a range of KK+ other than AA of course. A5s actually outperforms KK and AK against that same range.

Versus someone who is 3-betting way too wide, you can split your range into a 4-bet non all-in and a 4-bet jam range. For the jam range you use AK, AQ and medium pairs mostly for equity denial, but you're not always in bad shape when you get called. For the 4-bet non all-in you include the AA-JJ and some suited Ax for bluffs. You can sometimes omit the bluffs, since this player type is reluctant to fold both pre and post flop. The 3-bet size should be roughly 1/10 of their stack though. If it is only a 6BB 3-bet, you're not going to be able to implement this exploit since there isn't enough money in the pot. However if it is a squeeze spot or if you open BU 2.5BBs and they make it 11BBs from the SB now there is enough out there to do this.