In terms of how high level damage Is "balanced" (it isnt)... well okay so Id say there are 4/4.5 tiers of building in complicated TTRPGs like this. To be clear, all are equally valid, and all can be just as fun, etc etc. Also, im talking purely about big damage builds, which tbh in my opinion are usually the least interesting powerful builds in pathfinder, but if I start talking about other high level, optimized pf builds I will never stop, so Ill stick to damage. And Im putting a readmore because even Without getting started on the really fun builds like creating a feedback loop of infinite actions, I'm about to be Very autistic.
1st tier is someone who really does not have any system mastery, usually someone just starting out. Theyre mostly gonna pick options that sound fun and arent too complicated. When they level up, theyre gonna look through the most accessible options and pick whatever sounds cool or interesting. I cant actually put any good numbers on this tier just because Ive never had many players in this tier, and even when i have, i like helping players build more mechanically complicated characters that give them more options in play.
2nd tier is someone who mostly knows what theyre doing. They dont have any particular urge to optimize and dont go through every possible option, but they have a specific build in mind and mostly find good options. At higher levels in a normal campaign, in my experience, these guys (if built primarily for damage) tend to average ~120 damage per round against enemies at around their CR, give or take a bit depending on how theyre doing it/whether theyre built for reliability or are more well rounded, etc.
3rd tier is where I tend to build at, and where most of my players end up. This is players who have either a near encyclopedic knowledge of the options, or enjoy going through the prd for hours at a time to find the best options available. At high levels, again allowing for some variation based on other choices, these guys tend to average ~250-300ish damage per round, with the far end getting up to ~500ish (and if you allow mythic abilities, you can basically double or triple those numbers). This is where you need either all of (the combat focused members of) the party to be somewhere around the same level of optimized, or need a good gm, because it isnt fun for anyone if one player (speaking from experience as this used to be me) is dominating combat because the others just cant keep up. But if the entire party is at this level of optimization? Imo thats where pathfinder really shines. Being able to out extremely dangerous combat puzzles in front of a group of characters that are all well designed machines, who have a very good knowledge of what they can do and how to do it...thats why I stick with pathfinder 1e even though my group has come to the conclusion that a solid 15% of the game was written by giving particularly vicious chimpanzees access to typewriters.
4th tier is when you are no longer building to play the character, you are building in the hopes of raising the character high enough to catch a glimpse of the gods. This is where you get mages who can go all out and deal a quarter million damage in 1 round or a slayer who can sneak attack someone 20 times in a round. These are the characters that I have dreams about, praying that at some point in some campaign, Ill find a way to actually use them.
The weird 4.5 tier is cheating because its not really focused on damage specifically, but I want to give it an honorable mention anyways. This is the same as 4th tier, but instead of building specifically for big damage, youre building for something very specific instead, with damage as your metric for how well youve pulled it off. This is the tier where you see a weird ability and go "hmmmmmm" while grinning evilly. Examples here include stuff like "how much damage can i average in a round using nothing but magic missile (~360 iirc)" or "how many attacks can I give this summoner in one round? (~25 or ~50, depending on how stricly you interpret a specific ability.)" Some of these ones Are actually playable without wrecking a campaign, but like, itd be Really weird.
Also I lied because 5th tier exists and its the ones on My List, where you find something very poorly designed or not thought out and discover that making your character into a demigod only requires 11 levels in a specifc class and a friend willing to cast a random spell on you a few hundred times.