For how long are you staying? I think unless you have about unlimited amount of time, you should go to one area of the country and explore that area. If you decide to go to northern Norway, then make sure you take your time to travel all the way out to the end of Lofoten, for instance. The Narvik area and Senja island is fantastic too.
Actually the whole coastline from Trondheim to Bodø is super, but also there you should take your time to drive along the small winding roads off the main routes. Make sure to take some og the ferries out to the small islands off the Helgeland Coast.
Then there is the rest of the coastline from Trondheim via Bergen and Stavanger and all the way to Oslo...
Pick an area and stick to it. It is tragic to see all the german caravan tourists who push on for days and days to get to the North Cape, who have no time to stop and see the beautiful scenery off the main road.