If you pick up the rental car in Nice and return it at GOA airport you will pay hundreds of €uro in one international drop off fees. So you will save if you drive back to Nice, return the car and fly out of NCE. You can also take a train somewhere into Italy, pick up a rental car in Italy and return it in Italy. Both Savona and Genoa have rental,car offices from the major rental car companies.
On the Riviera di Ponente (western riviera, i.e. west of Genoa ) some nice places are Laigueglia, Varigotti, Cervo.
On the Riviera di Levante (eastern riviera), I like Camogli, Sestri, Moneglia, and of course the Cinque Terre, just to name a few.
If you are planning to retire in Italy know that there are huge tax implications if you become a resident for over 6 months in a calendar year. Income taxes are high in Italy (tax rates are 35% for global income over €28,000 ($32k) and 43% for incomes above €50,000 ($58k), under €28,000 the rate is 23%. Also there are no standard deductions therefore you don’t deduct anything upfront. If you are not an Italian citizen, your public pensions (like Soc.Sec.) are exempt and will be taxed by the US government. The above are the rules according to the bilateral tax treaty between US and Italy.
If you want to save on taxes the way to go is to retire in a southern Region (Abruzzo, Molise, Campania, Puglia, Basilicata, Calabria, Sicily, Sardinia) but in a municipality with less than 20,000 population in any of those Southern regions. If you make that choice Italy offers 9 years of tax free status.
There is also the “Uncle Scrooge tax regime for multimillionaires”. In such regime you pay €250,000 every year and you are done. If you make a couple of millions a year it’s a good deal.