Here you can have some information about the socalled national tourist roads of Norway: https://www.nasjonaleturistveger.no/no/turistvegene

As mentioned above - maybe ride through Norway one way and Sweden or Finland and even the Baltics the other way.

In Norway the main route north-south is called the E6. It starts almost at the southeasternmost point of Norway and goes through the whole country and ends in the town of Kirkenes, the bordertown to Russia. But E6 is a heavily trafficed road and especially during summer, and its maybe not the most exiting route either. So a good advice is to stay away from E6 as much as possible. I presume you might want to see some of the fjords of the westcoast such as Lysefjorden near Stavanger, you can take a ferry from Stavanger to the bottom of the fjord and ride a spectacular road up, or vice versa of course.

Further north you can ride through the Geirangerfjord, further north to Trollstigen, then the Atlanterhavsveien.
Further north of Trondheim you can choose Kystriksveien/Heleglandskysten and stay on that almost all the way to the city of Bodø. It includes 5-6 ferries so you better calculate that. From Bodø take a ferry over to the Lofoten islands, further through the Vesterålen islands and to Andenes, take a ferry from there (the whale route) to the island of Senja, cross Senja on the outer side/west side, then further a ferry to Kvaløya and then theres only 60 kms to Tromsø, the biggest city in Northern Norway. From Tromsø you can take the road via Lyngen which includes two short ferry hops, but will save you some very boring stretches on the E6. But from Olderdalen you will have no other option than the E6 a bit northbound.

Wildcamping is allowed in Norway as long as its 150 meteres away from nearest house, but not on farmed land or land used for grassing. Its always better to ask the nearest settlements if something is not clear.

Midsummer night solstice is a big thing in Sweden and a public holiday there, but not so much in Norway. So nothing to worry about if youre in Norway that day. Shops and restaurants will be open as usual.

Alcohol and tobacco are very expensive in Scandinavia, especially in Norway, so you better stuck up on that before coming there if you want to save some cash.

__________________
In the end everything will be fine. If its not fine its not the end....