I’ve just spent over 2 weeks in the Campania region of Italy and used an Artecard Lite extensively during that visit.
They are very easy to purchase now. Just go to the little “shop” (literally a desk in a small room) next to Tourist Information Office in Piazza del Gesu Nuova. It costs €26 and is valid for one entry to each site for 365 days. You get a pdf document on the spot (and they check to make sure you have it, no paper copies available). The document has a QR code that you show at the various museums, etc. No need to fluff around with apps, etc.
I’ve used it at about 10 places, including Pompei, Herculaneum, Caserta, Pozzouli, Paestum as well as Naples. You do not need to book a time for Pompei and there is a dedicated Artecard entry line at the Piazza Esedra entrance (a few minutes walk down the road from the station).
Note that this version of the Artecard does not include transport.