As skieurope has stated, self-study any AP adds nothing to your college application. Being a state or national AP scholar also means nothing to a college. Colleges want you to take the most rigorous courses available to you at your school, and none of them will be impressed by self-study of any AP, even the more difficult ones. If you’re truly interested in certain subject that happens to coincide with one of the APs, or want to get potential credit for some college course at certain colleges, study it by all means (for other benefit, but not for college admission) and you likely need to go much beyond what’s covered by the AP material/exam.