I personally don't like to rewrite people's itineraries and tell them that they have to visit the places where I carved out my memories. I believe that everyone should discover their own, instead of me telling them where to go so they can relive my mine.

Some people would rather go for a long, sweaty hike than to stay at a Michelin star place.

Maybe I'm wrong, but I thought OP was primarily interested in Bolzano vs Merano. My vote would be Bolzano. If it's too hot, which I doubt it will be because in Italy in July it's hot and everyone is still enjoying themselves, he can take the tram from the center of Bolzano to Soprebolzano, a city on a plateau whose name translates as, "over Balzano." It's around 4,000 feet high. The tram is a spectacularly scenic ride.

At Soprebalzano he can take the Ritten train, one of the oldest trains in Europe that was built for the Austrian Emperor. It's old, like traveling on a train from 125 years ago in an old black and white movie, spotlessly clean and maintained, that soars over alpine peaks and valleys, then he can be back in Bolzano by sunset.

Not everyone is comfortable getting off a cruise ship, renting a car in a foreign country, has the requisite international drivers license, and will be comfortable driving around the mountainous regions of rural northern Italy where they don't speak the language.

OP's research led him to Bolzano or Merano. It's his itinerary. I know he's open to other suggestions, but I'd recommend Bolzano over Merano. He can top off his cruise with a wonderful hotel stay and dinner where the cool mountainous temperature in the Bolzano evening will require a sweater or a jacket, in a place that is recognized as one of the classiest cities in Italy.