I have not done these excursions. We will be doing the Capri/Blue Grotto one out of Naples. We have done land vacations to Sorrento, Amalfi, Pompeii, and Naples. Missed Capri due to weather/ocean roughness. If you are a big archeology fiend, you could spend a lot of time at Pompeii. We aren't massive fans but enjoy it. We did Pompeii and Herculaneum in a day from Sorrento. I doubt the one with Pompeii would be enough time for a big fan.
We took a bus from Sorrento through Positano to Amalfi, so that we could both see instead of just the passenger seeing. This was in February, and traffic was still a nightmare. There was also road construction. We had to exit the bus, walk a few blocks around the closed road, and wait for another bus. Not sure if this would happen on a shore excursion though, but it is Italy. It can take a while to get around that area. I think we got back fairly late to Sorrento. Just doing Sorrento/Amalfi can be a lot.
Also, it's Italy. Don't expect anything to go quickly or probably even on time. They have a much more relaxed attitude about things than many other places.