medical/life choices/directions yeah sure 16, younger if meeting appropriate care and oversight guidelines.
Vooting? Fuck it, sure, 15.
Sex? Idk. 18-20 with similar rules as now (technically 16 for individual but within certain age range for partners), we're gonna do it anyway but goddamn we're so young and dumb at that age
Drugs? 25. Hard stance. Let that frontal lobe really come into its own first.