We chose a 12 day cruise that took us from Bergen up to the Russian border and back. Bad weather intervened on the return journey so we were stuck on board for most of the time and there's not much to do other than read, gaze out at snowy mountains, doze and eat. We would choose a shorter trip next time and fly back from Kirkenes.
Snowmobiling at Kirkenes was brilliant helped by glorious morning sunshine. Dog sledding was also worthwhile. Excursions are eye wateringly expensive but if you're only doing these things once.....
The ship was fine and the crew were very good. It is a ferry however and it stops everywhere along the coast taking on board cargo and passengers who use the ship like a bus service. Don't expect the luxury of a cruise ship and grab a seat before the locals come on board otherwise you'll have to revert to your cabin.
Double bed, window on 6th deck with unobstructed views, tv and shower cubicle including toilet. 6th deck is not the best place to be when the boat was rocking. Sea sickness sufferers better off lower down.