How I can Optimize this trip ?

You have amazing timing. "The French Riviera with Steve Smith" was the topic of yesterday's Monday Night Travel (MNT) (2/3/25). I watched it last night (in real time), and it was wonderful. You may find it helpful with your itinerary planning. This episode of MNT has not yet posted to the website, but it will be shortly. https://www.ricksteves.com/travel-tips/travel-classes/monday-night-travel

The link to previous MNT travel episodes, listed by country:
https://www.ricksteves.com/travel-tips/travel-classes/monday-night-travel/videos

I have not been to this region of France yet (on my wish list), so can't speak from personal experience. But, here are some nuggets from the MNT episode that may help:

1. Antibes is a short train ride from Nice, so would make a good day trip. If you want more city time, stay in Nice and day trip to Antibes. That's what I would do because there's so much that interests me in Nice, which may or may not be true for you. The main attraction for me in Antibes is the Picasso Museum.
2. Avoid Cannes and St. Tropez if you want to avoid the tourist crowds in places that are overblown.
3. Consider Antibes, Villefranche-sur-Mer, Eze, or Menton if you want smaller towns for a home base. The latter is closer to Italy, and may be too far away from places you might like to visit on day trips. But close to Monaco, which is not on your list (or mine).
4. I like his idea of having 2 home bases in the Riviera. I would likely do 4 nights in Nice, and 2-3 nights in Villefranche, but don't know how that fits with the rest of your itinerary.
5. He describes some inland places that you might consider, although most of those require a car.
6. Rick's favorite wine in that region is Bandol. I see that Bandol is a town on your list.

How much time do you want to spend in Madrid and Paris?

What do you like to do on vacation? You are targeting four smallish coastal towns (Bandol, St-Tropez, Cannes and Antibes), of which I've only visited Antibes. One thing I know is that there is no rail service to St-Tropez; getting there requires switching to a ferry, bus or rental car--and I have no idea what driving and parking conditions are like.