I'm just back from Naples on easyJet a couple of hours ago. Landing there last week (from EDI) I was lucky enough to be first through immigration so no delay, and waited about 5 minutes for bags. That might not be reflected in ATH or VIE however and you might be better asking in the country forum.

Departing NAP this morning I arrived < 2 hours before departure, checked in a bag (easyJet Plus check in), had a cigarette, did some shopping went through security and passport control (you won't have that issue) and was still at the gate well before it opened.

I wouldn't normally recommend this, but if I had chosen to cut it close on departure I would have had no problem. Personally I like to relax when travelling and give myself plenty of time.

One thing to beware of, don't trust the app messages to tell you the right departure gate at NAP - check the boards as well.