My DC took a different plan:
Grade 9: AP Physics 1 (it was literally an uphill task, realized later that it was too early)
Grade 10: Honors Chemistry (block 1), AP Chemistry (block 2)
Grade 11: AP Biology
Grade 12: AP Psychology
Overall DC took 15 AP courses in total (grade 9 – 12), 5 of them are medical related. Have seen one kid taken 17 APs in Fall 2021 BSMD results thread. Don’t know if anyone has taken more than 17 APs. However, some expressed opinion in BSMD threads saying that overall 8-10 APs may be sufficient for BSMD applications.
Never heard of self-study for AP Chemistry Exam. Experts can chime in on this.
IMO, you need to dig through the results thread to find out what kind of AP courses are taken by the successful BSMD candidates (some posted what they took) in the past.