We have 7 nights in October to split between Provence and the French Rivera. Trying to decide which area warrants more time? Also, is the Italian Rivera easily accessible? We might even consider using 2 nights there. We are only traveling via Train and will not be renting a car.
I would spend it one area or the other. Splitting the time gives each too little time go know and enjoy it.
Our visits to Provence have involved having a car, although on our first trip we used regional buses to get around a bit before picking up the car. Being able to drive lets you go to various villages and towns on your schedule.
In October, I’m guessing you’re not planning on lounging at the seaside a lot, so sights in towns, markets, museums, dining, etc. may be more on the agenda.
Depending on your interests, maybe split your time, 3-4 Provence days and 3 based in Nice? I’m not sure I’d cut time further, with just 7 days, to venture along the Italian Riviera.
The most scenic parts of the Italian riviera are East of Genoa, so quite far from the border : I wouldn't stray beyond the border.
The suggested 4d Provence / 3d Nice split is a good suggestion to me.