I think mostly power is very relevant to campaing style. Is it wilderness game, dungeon game, city game, very much fights or social situations kind of game etc.
Social min-maxers are for me kind of worst to balance in game where social situations are important, if these situations are mostly resolved by roll of a dice. It's easier to make challenging fights, than keep game beliavable and interesting so that super diplomatic and charismatic character could find much challenge in normal situations.
Sure there are many combos that can make character more powerful compared to core rule opitions. Sometimes those combos are kind of meant to be (powerful prestige class), and sometimes it's just weird combo aka FR+Eberron+Miniature's Handbook etc. And of course it gets even worse when books of multible publishers are added. But IMO it mostly gets worse in sense how weak, and boring and not worth it most of those new classes/spells/feats are.
My players and myself mostly use core stuff, because interestingly, it seems to be, where the best things are. And some stuff from elsewhere, so here are our most popular feats, weapons, classes, races and spells.
Weapons:
Composite Bows
Great Sword
Classes: Fighter, Ranger 3.5, or Fighter 4/Ranger X
Prc: Eldrich Master (Dragon Magazine), Blessed of Mesos (no-one plays sorcerer if both of those classes are disallowed)
Races: Human, Half-Celestial, Half-Dragon
Feats: Power attack (both editions), Cleave, Improved Favored Enemy, Improved Critical, Luck of Heroes (both editions), Karmic Strike (both editions), Improved Initiative
Spells: Varies, though it's wonder, if spells Magic Missile, Greater Dispell, Teleports, Dimensional Anchor, Harm/Heal, Horrid Wilting and Polymorph Other (Baleful, I just like that original name more) won't eventually appear if there is high enough level caster in party.
See, my players like their power-gaming simplied. Not going through too many books and all.