I have about 3 weeks vacation, travelling solo, that I'd like to split between a few cities in Switzerland and the Provence area. Provence would be my main focus, with the leftover time to be spent in Switzerland (I've already been to most of the cities, this would be to those that I missed last time). Currently I have about 12 days budgeted for Provence. Is that a good amount of time without rushing? Or too much time?

I'd like to visit Aix-en-Provence, Avignon, Cote D'Azur, Marseille, and any other nearby cities and towns which should be visited. I'd like to avoid renting a car, but I'm open to it.