I think "balance" is basically the difference between poker for the long term and poker in a vacuum. If you are playing vs a thinking player on a regular basis then he will be looking for exploitable holes in your strategy (as in, he never does this with X, and never bets the turn with Y etc) to counter his attempt to exploit our play we are trying to give him zero situations where he can rule out any type of holding. "Balanced Ranges"
There is no reason to think you wouldn't run into a player capable of this at lower stakes, it's obviously true to say that the higher stakes you go to the players of this quality you'll run into, therefore meaning a "balanced" strategy should be more at the front of your mind. You need to identify the players on this level and attempt to play as un-exploitably as possible vs them, even at lower stakes, with balanced ranges in every spot possible.
Vs non-regular opponents or obvious weaker players who most likely aren't going to notice exploitable gaps in your game then for sure you should always play optimal vacuum poker, as in just make whatever play/decision you think will yield the most profit in this specific spot, this way of playing will almost ALWAYS be more profitable, as you aren't making immediate concessions in the hand for future benefit, basically what "balance" is in practice.
Defo don't think though that weaker players aren't capable of spotting trends in your play though, because they defo are (he always bets big when he has a lush draw etc) but they will often be EXTREMELY biased by the short term, so defo bear that in mind.