Air BnB Recommendations

I stayed in a little apartment in Juan les Pins. It was close to the train station and a couple blocks to the beach. Depending on what you're looking for, I'd recommend Antibes. I found it to be the nicest town on the Riviera, nicest sand beaches, best medieval center with cafes in a market square, nice marina and small. Nice is a big city. Villefranche gets a lot of cruise crowds in a small space. Cannes is fairly large also and pretty far out of the way. St. Tropez is even further from other Riviera towns.

If you Google "tourisme French Riviera" or "tourisme Nice, Cannes..." and other cities you may be interested in you will find tourist lodging, hotels, and AirBnB's.
Not certain that anybody has stayed in all 4 cities.

Saint-Tropez has no rail service, so you'd be on a bus for over an hour just to get to a train station. For me (I depend on public transportation in Europe) it would be a very inconvenient base.

Nice is superior from the standpoint of transportation to other destinations along the Riviera and in the hills. I loved having so many things to do right in the city, but it is a large city, with a vibe quite different from what you'll find in the other places you listed. Villefranche is very small (would be too small for me to stay in), and I did not go to Cannes or St-Tropez. I especially liked Menton (but it's all the way over near the Italian border) and Antibes.

A lot depends on how you plan to spend your time. For example, I don't do beaches but enjoy art museums, gardens and markets.

Thank you and thanks acraven I was not aware of this, i will give St. Tropez a miss as I will not be driving on this trip.

Antibes looks fantastic.