French Riviera 2019

I can't advise on specific campgrounds, but there won't be anywhere to stay a campervan in Nice itself. However you will have a few options between Nice and Antibes (more convenient), as well as inland towards Vence. This being said, I have two question for you.
- Do you have to have that campervan with you? Such a large vehicle in the French Riviera in summer will be... inconvenient to say the least. To explore the sights bewteen Cannes and the Italian border, as well as some inland locations like St Paul de Vence, public transportation is much more relaxing and quite efficient. If you ditch the vehicle and don't mind a very urban environment then yes, Nice is the best base.
- Does it have to be the French Riviera? Nice is a 4.5-5 hour train ride or drive rom Lyon. Provence (Aix, Avignon, Arles, Cassis...) is much closer, July is lavender season, and a vehicle will be much more useful there.

I agree with the prior poster, a campervan would be a large liability in mid July, the peak holiday season, in the more urban areas of the Cote d"Azur. You are better off in the countryside, perhaps in the Luberon or Valensole, or in the Var. Are you actually going to camp?

If you are intent on going to the Cote d'Azur, I've seen a nice campground not far from St. Paul de Vence, near la Colle Sur Loup (Camping Les Pinedes). But I've not stayed there, just noticed it on my drives. A better approach might be to stay close to a public transport link, perhaps a train station, so you can see the coastal areas or at the least stay close to the A8. For example, many of the campgrounds are near Biot, which as a Gare. The downside is that this is all very close to Marineland (and a Waterpark) so they quickly fill up -- the village itself is charming but the stuff in the lowlands less so. If you are not camping , then you can stay at a gites, B&B/Mas, with good parking perhaps near St. Paul de Vence, Cagnes Sur Mer, Mougins, Beaulieu or any town closer to the A8. (Note there are also park and rides in Nice, to get to the center without driving). Some of the coastal towns can be really tough to get around with a large vehicle and in/out to the A8 problematic with traffic in July.

Campervan, yikes !!!! I had a slightly wider than compact car on the riviera a couple months ago and it was harrowing driving through the narrow lanes in some towns . . . many times I found myself literally between a rock and a hard place, with stone buildings on one side and a 2 meter high stone wall on the other, and not enough room for a person to walk past the car (and outside mirrors safely tucked in). With my own car I wouldn't have worried about scratches and dents, but in a pristine rental car it's a totally different feeling. I found parking in most places in March for the car, can't imagine what it's like in July or trying to park a camper. Train service along the coast is convenient and cheap and no traffic jams. The train stations are all walking distance to the towns. Only in Nice did I use city public transport, several times on the tram when I was too tired or in a hurry, and the bus once to get to/from the Chagall Museum.