From Google camera looks like the E4 has a mix of dual carriageway/single carriageway.
So if you want to get through Sweden quickly (as the roads are so straight!) looks good.
When coming back down from Nordkapp (admittedly via Kirkenes and the Russian border) I chose the E45.
Sort of Karasjok (in Norway) then Gallivare down to Ostersund - the 'middle' of Sweden thinking it would be more scenic.
If you are into tall trees stuck close to each other with the odd bend in the road - this is the route for you.
Advice? IMHO, get Sweden over with asap and save your days for Norway.
BTW Finland IS a lot of lakes and yep, more trees.........
Cost to 'enter' the Nordkapp centre was about £25 in 2011.
So save up for that too!!
If you've gone that far....it's only equivalent night's camping or so
I think the Nordkapp pass is valid for 48hrs
(citation needed)
So you could camp out and get that iconic picture of the midnight sun and the globe.
Then enjoy Norway's fabulous west coast!!!!!!
Challenge: keep off the E6 as much as possible!