It is important to me that the PCs be roughly equal and, while heroes, are not world-shaking heroes before very high levels.

This is partly to avoid one PC being the center of attention in a party. Therefore, backgrounds like chosen ones or lost heirs are probably not okay. They might be if everyone has a rare background but it's hard to make that work well.

Exemplars by their nature make the PC special over others, plus my understanding it is one of the less well balanced PF2E classes so those are not available to play.

We won't be playing with mythic rules. I think a campaign needs to be structured around the mythic concept to work and I'd like to run a campaign focused on the premises you'll find in the campaign options.