The most direct route from Orlando to Miami is via Florida's Turnpike. Unfortunately, it is extremely rural and there isn't much to see or do. Even in South Florida, the road runs well to the west of much of the built-up areas so there isn't much to see here either.
You might consider switching over to I-95 when you get to the Fort Pierce exit. Continue south then on I-95 and exit at Palm Beach Gardens exit signed as PGA Blvd. Heading east here takes you onto State Road A1A and then down to Palm Beach where there a many millionaire houses along the ocean. i.e. the Kennedy compound. SR A1A from North Miami Beach down to South Beach can be interesting due to all the old art deco buildings. Or maybe not.
BobK/Orlando