Rental Car from Paris to Nice

How much time do you have for this trip? If it is just one day, my advice is to take the train. In any event, I have not found any rental car company to be any better than any other except that Avis charges one-way fees. If I were driving from Paris to Nice, I would just pick the rental car company that is closest to my starting point.

All the majors are equally unreliable. Go for price. Be sure to use a credit car that includes rental car insurance. Buying it from the rental agency is robbery.

the French word for a stop sign is "STOP" not Arret as in Canada,

Expressways are fast but very expensive tolls.

Usual International road signs with one exception, the priority road sign of which there are two types: A priority road sign with a black slash across it is a Yield sign, meaning you are on a non-priority road and must yield at the next intersection which will be
a priority road (it's traffic has the right of way). If your road has a priority sign without the black slash, it means you have the right of way at the next intersection. I think I remember this right, but check it out.

There are a lot of roundabouts with uniquely eccentric directional signs. the system will eventually make sense.

Of singular value in France are the Michelin maps & Green Guides (specifically designed for sightseeing by car).
Get the 1/200 000 scale map. It shows roads, scenic roads, sights to see (rated).

I prefer the older Green Guides (ink drawings instead of photos) to the newer one with photos. Try eBay. Get the regional Green Guides (Alsace Lorraine Champaign, Auvergne Rhone Valley, Brittany, Burgundy Jura, Chateaux of the Loire, Dordogne Berry Limousin, French Alps, French Atlantic Coast, French Riviera, Languedoc Roussillon Tarn Gorges, Normandy, Northern France & the Paris Region, Paris, Provence and Wine Regions of France to where you will be.

Route recommendation: The Route de Vin Alsace is one of the top drives in EU. I've done it about 10 times & never get tired of it. Did it last November, & I'd go back tomorrow. GO east from Paris to Rhiems to Metz (not a great sight. Skippable) Then take the expressway over the mountains to the rhino Plain & Route de Vin Alsace If you want to visit Strasbourg, the N4 is an easy route to a big parking lot near La Petite France. I prefer smaller Colmar to Strasbourg.

Kaysersburg is one of the gems on the Route de Vin. there is one bus a day from Colmar, M-F. No weekend service. that's why this is a car trip.

At the end of the Route de Vin, head southwest to Burgundy, then south to Lyon & Provence. If you want to go into the Alps, one of the world's great mountain views is at the Oratorie near Chazaulais (see Green Guide Alps) which is all but inaccessable except by car.

On reaching Nice, keep your car for the drive to the Perched Villages, especially Eze Village, the one on top of the cliff, not the Eze on the coast road. I think I looked it up once. there are only 3 buses a day from Nice to Eze. Best done by car.

I've suggested 3 great sights that are for practical purposes, only accessible by car-- Route de Vin Alsace; Oratorio, & the Perched Villages. Since you have a car, do the car stuff.

Also, don't miss the Roman ruins in Arles--Orange--Nimes

Your question doesn't make it clear: If you just want to get from Paris to Nice, take the train. Having a car in Paris or Nice is highly counter-productive.
But if you intend to use the car on your way to Nice, to explore some of France that doesn't have regular train service, that makes sense.

If it is a single direct journey you will more in tolls alone than the train would cost. Plus all the other things that add costs in car rental, including the rental itself. If you are not from the EU you are also required to have by law either an official translation of your driver license or an IDP (IDP cheaper, faster, and easier, around $20 US or equivalent from AAA/CAA).

Parking in Nice is awful.

All the majors are equally unreliable.

That's the best line I've seen so far today! I've found that some rentals have gone smoother than others. But I think it depends more on the individual agency (or the agent) than the name of the company. Or the way that the stars are aligned that day.

While I've heard of issues people have had with the major agencies, more often than not the biggest issues I've heard have been with some of the smaller, lesser known agencies. But YMMV. I've never had an issue, but primarily use Hertz (and on the Nice side), where I have a loyalty program status, which I think helps deter issues.

FYI, note there are 14 buses (82/112) every day between Nice and Eze (le village). 8 now on Sundays. However, the car drive does provide some amazing vistas.