I have only done the Hurtigruten cruises along the Norwegian coast and also into Svalbard . Saw Northern lights both times on several nights .
The coastal Norwegian Hurtigruten is a passenger ferry taking Norwegians along the coast as well as tourists . You stop at many ports, some for only 15/20 minutes . There are the coastal experience teams who do some talks but mostly you amuse yourself . Food, some drink is included but excursions are not. However most stops are in town/village centres so you can do your own thing in most places.
The Hx expeditions just have tourists , they have lectures on science, culture,wildlife, science labs on board , they stop at far fewer places so you can explore, they have some excursions included (normally one in each stop) , and do landings on small inflatable zodiac boats as well as carry kayaks . Again there is no “entertainment” as such other than the lectures , science etc and people tend to read, craft , play games in the evenings . Both types of boats carry 300 to 600 people .
Food is excellent they pride themselves on using local food , so they may pick up local cheeses at a port, or seafood etc.
They are not cheap , but you can , in theory , pay nothing else and it’s a lot cheaper than staying on the mainland.
Much of the joy is staying on deck watching the scenery and wildlife … whales, dolphins , puffins, walrus , polar bear (Svalbard) . You can have an alert in your cabin if the Northern lights appear, whatever hour that is.
It is great if you want to see the scenery, wildlife and understand about it. It is not for you if you want shows, entertainment , night life and dressing up. Take binoculars , warm layers and an open mind .