Ideal high school course load/schedule for a wannabe Princetonian?
The most challenging that your school offers.
I assume my son’s course load was fairly typical. Here’s my off the cuff recollection of some of the AP classes he took junior and senior years:
Chemistry
Calculus BC
English Language
English Literature
Spanish Language
Spanish Literature
Art History
European History
Biology
U.S. History
Physics B
Physics C
Keep in mind that Princeton won’t penalize students whose high school’s don’t offer a lot of APs, as long as they take, as @Cantiger wrote, the most challenging offered.
A rigorous, challenging course load that genuinely excites you for its own sake.
Here are Princeton’s recommendations for academic preparation:
https://admission.princeton.edu/applyingforadmission/academic-preparation