How much should we be 3-betting BvB in an optimal gameplan?
I don't think too much about this stuff when playing lower limits. I 3-bet as much as I get away with and assume opponents make plenty of mistakes post-flop.
I'm interested at hands like KQ/AJo specifically. Then hands like QJs/KTs which could be 3-bet immediately for fold equity.

The problem with 3-betting is that we fold out most of the weaker (dominated) hands. For example KQ. Not everyone continues KJo preflop, so our opponent has K9s-KJs that we beat.
3-betting AJs would fold out all of the many Qx Kx Jx suited hands from opponents range. Also hands like J8o+

Position has to be taken into account as well. The reason why you would want to 3-bet a lot heads up is that you will always be OOP in the BB.
In BvB the situation is reversed. No hand loses value due to positional disadvantage, instead it only gains.
Good argument for 3-betting those hands mentioned is that they will be very profitable fold equity wise. But can you gain more EV from playing post-flop in position?

On the other hand, it may be good to fold out opponents equity right away preflop. For example KQ may lose to K8o on K8x board, but on 3-bet pot you would only see K8s (if even that).
And now lets say AK always 4-bets preflop, so KQ would literally be the nuts on K high board.

Players post-flop skill has to be taken into account as well. A weak post-flop player should lean more towards 3-betting.
Post-flop can be divided into 3-bet pots and single raised pots. If player knows 3-bet pot strategy, then for sure he can exploit his opponent in a bigger pot. I think the problem is that everyone has a good idea what to do in 3-bet pots since it's the most studied spot. You might have the most comprehensive 3-bet pot strategy, and make the most simple mistakes in single raised pots.
So from this standpoint, it would come down to how much (or how often) you can exploit your opponent.
I think there is more exploitation possibilities in SRP's, but in 3-bet pots the pot is much bigger.

Any thoughts?
Here's the hands I talked about: KQ AJ KTs QJs

15-20%

I don't think the bold is as much a preflop concern than it is a postflop concern.


I'm not sure. However some stuff comes to mind when I read this question:

I think that it's almost entirely dependent on both the opening range/folding range/calling range/4 betting range of the opponent, which should be, but isn't necessarily the case vs humans, dependent on stacks.

for example:

folds to the small blind, he raises 3x with 47bb behind. I cover.

I'd 3 bet this as default to 9bb: 88+, AJo+, ATs+, A5o, A5s-A2s, KJs+, KQo, QJs, JTs, T9s, 98s.

compare that to this situation:

small blind opens 3x with 97bb behind. I cover.

I 3 bet this range as default to 9bb: 66+, ATo+, A9s+, A8s-A6s sometimes, A5s-A2s. A5o, A4o sometimes, A3o less often, A2o even less often, KTs+, KJo+, QTs+, J9s sometimes, JTs, T9s, 98s, 87s, 76s sometimes.

3-betting KTs, A7s-A9s, KJos, ATos seems bad against most competent opponents. If they fold, you had the best hand (or flip), if they call, there is a good chance you are dominated, and if they 4b, you have to fold. Assuming something close to BE when they call (maybe this is pessimistic with position, but again, lots of dominating hands in their calling range), and assuming they fold 60%, call 20%, reraise 20%, then 3bing ends up being basically BE, as opposed to flatting which must be +EV since you have position and are slightly ahead of standard SB opening ranges.

Imo it is better to make these mergy type of moves OOP when it's harder to maximize a middling hand's value. IP, stick to a more polarized range of clear value and clear bluff.

We probably put the small blind on different ranges to start.

Yes I think this is quite pessimistic. I get much more action than your post suggests precisely because of the hands that I 3 bet.

Not sure if this adds up to a breakeven play even with my worst hands because I'm going to win often when they call the 3 bet.

I've heard this argument but I never really agreed with it. If I had to choose the preflop action that I believed would allow me to 3 bet at the highest possible frequency? I would choose sitting in the big blind vs a small blind open. Then from that perspective, my range shrinks as we go down the list:

small blind vs btn open
big blind vs btn open
small blind vs co open
button vs co open
big blind vs co open

However, I'm far from fixated on any type of frequency. That's just what I do readless.