I use both of these things, sort of. But I also use other things to determine who's weak and who's powerful.
- Class Level: Almost every person in the world is class level 1 at most. Only the most impressive get past level 3-5. I can count the number of mortal NPCs in the world who have 7 class levels without taking off my shoes. So adventurers who adventure for awhile are awfully powerful by mortal standards. Especially because I apply the CR system as it's written, which means characters, by fighting monsters which are weaker than they are, can get more XP from me faster than they get from most DMs; I think I might stop being quite so generous with XP. (Even though there are no NPCs above class level 7, items which require higher levels to create are plentiful. Don't ask how that happens.)
- Point Buy: PCs and the most naturally talented NPCs start with point buy 30. Most NPCs start with the Standard or Nonelite Array, or with point buy somewhere in the 12-25 range.
- Class Tier: The overwhelming majority of NPCs are Commoners. Of those that aren't, most are other NPC classes like Expert or Warrior. Of those that aren't, most are other low-tier classes like Samurai and Fighter. Some are mid-tier classes like Bard or Factotum, and a handful of the most skilled are high-tier classes like Cleric or Wizard. This, more than class level or point buy, is why churches and cults and mage guilds and the druids who rule the Elves wield so much power.
- Divine Rank: The gods have divine ranks. Because I prefer smaller numbers, I'm inclined to limit my custom pantheon in the same way I limit class level: every god is divine rank 1-5. I've also been considering a system where gods (and only gods) get to gestalt, probably with racial HD or between a high-tier class and a low-tier class, or between two mid-tier classes. (These two things make gods much more powerful than even the most powerful of level 20 PCs, but still in theory defeatable by the most powerful mortals.)
I think I'm going to limit all characters to at most class level 20 (10+ already being epic in this campaign). E20 is kind of a silly concept; nobody's ever going to get that high in the first place in this campaign. But if they do, then they can start advancing as deities. If it ever becomes a thing, I'll come up with rules for doing that. Maybe once you ding 20, you gain divine rank 0; that way, everybody gets a capstone even if their class doesn't give them one. Perhaps at level 20 you stop gaining experience altogether, though you're free to keep gaining gold, and advancing divine ranks depends only on RP. Maybe there'll be a way to gain divine rank 0 through RP before hitting 20 if any players are inclined to seek it out (perhaps by killing an existing god). Maybe you get to gestalt if you hit divine rank 1. These are all interesting ideas.