Southern Italy to Sicily

Southern Continental Italy is made of Puglia, Campania, Calabria, Abruzzo and the mysterious Molise. It's 28,272 sq miles, if you prefer.

You should first decide what you are interested in. Roman ruins and clifftop villages? Greek Temples and Beaches? Bears and... more bears? Olive trees and baroque towns? Cave houses? Seaside villages where nobody speaks English? Seaside villages where everybody speaks English?

Regarding Sicily, are you going to rent a car there? If not, a tour may let you see more in less time.

Southern IT comprises of Rome, Vatican City, Orvieto, Naples and the Amalfi Coast. For southern IT you need:
Rome – minimum three nights. If you visit Vatican City and Orvieto as day trips from Rome, make it five nights. Naples, too makes a good day trip from Rome and if so, make it six nights.
Amalfi Coast – if you visit the Amalfi Coast see Naples from here not Rome. Naples deserves a full day and so does the Amalfi Coast. You need a minimum of three nights and if you add Pompeii and Capri you need to add a night per day trip i.e., five nights. Good places to sleep are Naples, Capri, Sorrento and Amalfi. If you don't sleep on the island of Capri then skip it.
Sicily – you can take a direct overnight train from the Central Naples train station (10h) which I did once and barely slept but it was better than wasting a full day trying to get there. Rent a sleeper car if doing so and make your first stop Syracuse. You need a minimum of two nights in Syracuse. If you add day trips add a night per trip.
From Syracuse take a direct train to Palermo (4h 45m) for four nights. You want to visit the Monreale Cathedral (30m by direct bus). You also want to visit Cefalu one day (1h).
This itinerary requires 14 nights in IT and does not include the flight over.

We flew to Rome and changed planes for Bari. Then we traveled to Polignano a Mare for ten wonderful days as a base for exploring Puglia. Then we flew non stop to Palermo on Volotea for a self tour of Sicily which we had canceled twice due to illness. This combination worked very well for us and I highly recommend it. We spent two and a half weeks in Sicily , our second time there.
We rented cars.

If you are thinking of taking one of the Rick Steves tours, I would recommend the southern Italy tour as the places it goes to would be hard to do without renting a car. Then if you wanted to go on to Sicily, at least renting a car wouldn’t mean much driving for you.
We however took both tours back to back this past April and May. They were wonderful!

FYI Nancy--

We are considering an October 2023 self-tour of ~14 days. Flying into Rome, connect to Catania. Transport to Siracusa/Ortigia (3 nts). Train to Taormina (3 nts). Train, ferry, train to Salerno (3 nts). Train to Rome (5 nts). Fly home from Rome. We have visited all these places previously except Siracusa/Ortigia.

I've been told trains on the east coast of Sicily are reliable.