sounded to me like on certain boards where there's a low SPR and your hand is just a complete whiff, i.e. k6hearts in that example, its ok to just check give up and not continue to bluff at it...personally, when i find myself in those spots I want to continue betting as Im clearly not winning if I don't bet, but sometimes just giving up is ok

We need to have x/folds as give ups, especially on boards that are disadvantageous for us as the PFR. Also a principle that applies generally on later streets in all configurations.

The idea that balance is for playing against adaptive players. If I notice that you never bluff then I start folding bluff catchers or you always fold so now I always bluff. If your opponents play a fixed strategy then we choose the highest EV strategy. Whereas if our opponents can notice our tendencies as well, then we need the choose a strategy that isn’t particularly obvious what we do. It can be accomplished in two ways. One is balance, the other is swing strategies drastically based on game-flow. Early players preferred the game flow based strategies. More recently most pros have chosen balance. The game flow argument is higher risk, higher reward. The balance strategy is more geared toward high volume play where understanding metagame is more difficult.