I have done bits of the North Sea Route, the netherlands part and some touring in Norway.
In the netherlands the prevailing winds are from the southwest which suggests a counterclockwise route, but I can't speak for the other countries.
You can camp anywhere in Norway as long as it is on un cultivated land and at least 150 metres from the nearest building, for no more than two nights. I found that along the coast much of the land is occupied and around the fjords level ground is scarce. Nevertheless you should be okay if you are discreet, there is lots of forest cover.
I don't know about stealth camping in Holland its pretty crowded country , however anything is possible. I suspect you may have to search hard for campsites.
After talking to people in Norway I headed North to the fjords and the Lofoten islands, most Norwegians recommended that part of the country as opposed to the North Sea route. I still would like to complete the North Sea route some day.