From Napoli Porto Nolana to Sorrento by Circumvensuvian sounds more hectic than other Italian trains. I see the Orari Treni Campania Express is an option. Is this truly a better choice or should I just go by fast ferry?
Bob, how are you arriving in Naples? If by train to Napoli Centrale, I'd take the Campania Express if you really can't deal with the Circumvesuviana (which we've taken without incident). The trains to Sorrento depart from adjoining Garibaldi station so you wouldn't have to transfer to the port for the ferry.
The only caveat is that there are few daily departures for the Express, and the ferries aren't much better so you could have a bit of a wait to catch either one. The Circumvesuviana runs much more frequently.
If arriving at the Naples airport, I'd take the Curreri bus.
https://www.curreriviaggi.it/en/naples-airport-shuttle