Should I buy AppleCare+ up front or monthly on new iPhones?

I live in the USA and I am buying five new phones for my family: 2 iPhone 15 Pro Max and 3 iPhone 15. Since they’ll be on 36 month payment plans through Verizon I’d like AppleCare+ coverage for that term as well.

I have two questions:

1. If I do the monthly-pay plan on each phone will it stay active for the full 36 months?
2. Or could I buy the up-front-pay two year AppleCare+ plan for each phone and be able to extend the coverage on monthly-pay after they expire?

Paying upfront for two years of coverage and then extending coverage for another year on a recurring monthly plan would cost less if that is an option.