- Flat to gentle rollers. Maybe a little monotonous compared to other routes. Probably a good choice for a first trip.
- Camping will run from free to 10 euro (or more in some places) or so. If you ask around, you'll probably be able to find farms or something in NL to camp. I'd guess less likely so in DE. wild camping frowned upon, but doable. In DK, you can either find free camping places or special places where people offer cheap camping for cyclists (20 crowns a head, max). Go here:
http://udinaturen.naturstyrelsen.dk/udinaturen/
click on overnating and zoom the map. Frie teltningsområder means free camping. Primitive overnatingspladser are private places with max 20 crowns. I don't see an English option, but you can click and get a phone number and most people will speak English just fine on the phone.
- it will be windy and often rainy (unless you get lucky and find a week of sunshine).
- Nothing to 'skip'. The 'burbs will all have cycle paths to get you in and out. Bremen, Hamburg are common destinations. Ribe in Denmark is cool (Viking living history). Roskilde has a great Viking museum. I don't know where the route goes, but Als - Ærø - Langeland - Lolland beats Jylland - Fyn - western Sjælland.
Have fun.