Miami, not Miami Beach, is a bustling city. The restaurants are delightful, much quieter than those in NYC. Reserve Tam Tam 2-3 weeks ahead.
It is second only to LA for contemporary art museums. Many are free or half the cost of any in NYC. Try the Rubell, Margulies, Perez especially!
Visit South Beach for the art deco architecture. That is close by in Miami Beach. Uber worked well for us.