The AP players guides appear to be off limits, and any mechanics or items in there for adding campaign flavor look to be banned for core campaigns. Probably want to make access to the player guide a standard boon in the APs.
Hmm, are ethnicities (eg Shaonti) and even suggested names (eg Ancrym) from an AP guide non-core character options?
You can name your character whatever you like. You can also be a Shaonti warrior for roleplay purposes. You just can't get any mechanical benefits from choosing Shaonti warrior from a book outside of core. As a matter of fact, your character can utilize any of the countries in the Inner Sea World Guide for RP flavor. They just can't take any of the mechanical options from the ISWG unless it appears on a Chronicle (or when we update the Guide if we add languages and the like).
That's similar to what exist now without a sourcebook. I've had a character at a table I GMed that claimed he was from Arcadia. He had absolutely no mechanical benefits from it and it was strictly roleplay flavor, but he advised his character was from Arcadia. The same applies when someone says their character is royalty or a Blakros family member and the like. If something is taken for fluff only, and strictly roleplay purposes, you can use any of the source material. You just can't take any mechanical benefit from it.
This is just so awesome that I'm gonna print it and frame it...