You probably miss so much nice roads and sights by going E6 you'll have to come back one more time to see what everyone else is talking about Chef
If you're in a hurry go E6 if not take the outer road e.g. Road # 17 from Steinkjer to Bodø and so forth...
We are taking a similar trip the same way this year basically, but I want to get the most out of the ride up by hitting as many nice MC-roads up as possible without going twice the distance.
Also a bit risky going this early, we have snowfall still in Southern Norway (6th of May) and a lot of icing and snow as further up you go, several roads are still closed (even in South) as they still have not cleared them for snow. Keep an outside temperature gauge on the bike and if you see 4 degrees plus or lower beware of icing.
Best of luck on your journey...