Parking des Pecheurs near the Oceanographic museum has elevators/escalators to the top level where you can access the palace, cathedral, and old town. The Oceanographic museum also has an elevator.
There is rush hour traffic into Monaco before 9:00 and after 4:00.
La Turbie is known for its great views of Monaco, but scary drive. Most cruise passengers flock to Eze for its amazing views, although I would only go if it’s before 10:00 am.
It’s hard to find a good restaurant in these tourist areas. If you are driving from Cannes, maybe you can stop in Antibes on the way for lunch.