I live on the North Sea route, but I have gone only short distances of it. Since this is a coastal route; if you're bothered by headwinds you might want to check prevailing wind directions at "tour date".

It might be worth considering that the North Sea area is more than a bit different from the Mediterranean area in climate, landscape and culture.

In Germany/Holland/Belgium the bike path network is fantastic, with dedicated bike paths literally everywhere, so some of the easiest biking is to be had there, I feel. I didn't really use a map half the time, because it's an easy place to be.