Probably amongst the cheapest and best for a youngster would be Hurtigren. Not a luxurious cruise ship but the know Norway better than anyone else.
Discover the highlights of The Coastal Express with Hurtigruten. Explore the historic route, breathtaking landscapes, and unique experiences.
www.hurtigruten.co.uk
Hurtigruten had a monopoly on the route between Kirkenes and Bergen (with numerous stops along the way) but there's now a competitor in Havila which commenced sailings at the start of 2022 with a fleet of 4 brand new ships. They are partially electric. The two companies now share the route equally, sailing on alternate days with identical itineraries.
You can embark or disembark at multiple places down the coast depending on how long you want your trip to be. The full Kirkenes to Bergen (or reverse) trip takes 7 days but you can do as little as 1 day if you want.
In August last year we stayed in Tromso for a few days and sailed with Havila from there to Bergen over 4 days.
I think Havila wins easily over Hurtigruten. They are new to this passenger route but they have been in commercial shipping for many decades so they certainly don't lack experience.
The Havila cabins are very well appointed and have an excellent layout (much better than Hurtigruten's). Hurtigruten's boats are all 1980's / 1990's vintage and it shows, even though they have been refurbished over the last 10-15 years)
Havila's food & general service was excellent and I have no criticisms of their product at all.
For us Havila's the way to go.
www.havilavoyages.com
Quickstatus, there are seasonal changes to the route so you should look closely at what places the cruises call at for the dates you want to travel. One significant change could be whether the boat travels up Geirangerfjord which is one of the most beautiful of the fjords.
Plus, the route NS is not identical to the one from Sth to North.
I think lack of time will be your biggest enemy. Norway has such amazing places to see that we hired a car in Bergen after our cruise and did a 9 day road trip up as far north as Andalsnes and then in a big loop south to Stavanger and then back to Bergen and also had 3 days in Oslo. All up we had 18 days in Norway and we kept on the move the whole time. We could have easily filled in another week there.