The end of PreCalculus is definitely the best time to take Math 2. Both of my kids took it in 9th grade. Studying Calculus won’t really help with Math 2. If anything one may need to review the Math 2 material that’s not used in Calculus. I know a few other kids who are strong in math and who took SAT Math 2 as freshmen and received 800.
As for regular SAT, I would probably wait. DS22 has a great score from talent search from 7th grade (great enough that I wish schools would just accept his scores from middle school), but we will probably wait till this summer or his junior year to have him take it again.