So this is where you've been hiding.
We got back from the Ruhrtal Radweg yesterday. Don't know how helpful this will be because we went in the opposite direction and took five days religiously following the signs. Assuming you've got or seen the bikeline book:
The route is a mixture of bike paths, quiet lanes, compacted earth, loose chippings, crushed shells, all designed to keep you away from traffic. Not the fastest or most direct route but very pleasant cycling. The bike paths are usually shared pavements, which can be a bit of an irritant. Where you ride on the roads themselves, drivers are patient and courteous. We took five days but you could do it in two if you left the campsite before 12 noon.
The first 20 km or so from Duisburg to Mülheim is built up but after that it's all countryside. The stretch to Herdecke is flat, the Ruhr being contained by locks and dams so that it looks more like a series of lakes than a river. This stretch is very popular and we were told not to try it in the weekend, when half the middle-aged male population dons lycra in search of bier und currywurst. Schwerte to Bestwig has a couple of hills (15%-16%) but nothing too long. Olsberg to Winterberg is lumpy and rises steadily.
Signposting is excellent, you could do it without a map. The signs take you around and past all the towns and villages, not through them. If you want to visit a particular place, search for bier und currywurst or take a photo of the fachwerk houses, plan ahead because you will pass many places without realising it.
There are some roadworks near Mülheim and you will be diverted. The temporary signage is not all that it could be. The dam over the river at Werden is closed to cyclists until October. There is a bridge about 1 km before it that will take you into and through the town. That's the end of the traffic news.
Holiday season proper hasn't started yet in Germany and some bars, hotels &c were closed. Most villages and quite a few towns were deserted by about 8 o'clock (especially in the east). Some campsites were also closed, including the one at Delecke on the Möhnesee. The campsites might determine how far you go each day. We stayed in Winterberg, Hennesee (south of Meschede), Süd Oefer (Möhnesee), Schwerte, east of Werden and in a hotel in Ruhrort. Without exception they were all spotless, well maintained and had lashings of hot water. On-site shopping and eating facilities were poor, though. The cost for a night's stay was usually between 23 and 28 euros for three people and two tents. The only exception was Schwerte: €5 per person at the canoe club (recognisable by the canoeing gates in the river as you enter the town). Ask at the clubhouse and they'll let you pitch a tent on the grounds and leave the clubhouse doors open for you!
If you are going to Möhnesee, be aware that it is a long, steep slog from the Ruhrtal Radweg through the forest. Going across the dam itself will add another 10 km before you get to a campsite (NB the dam itself is only about ½ km long). Unless you want to take a very roundabout route back to the Ruhr, you have to follow the same path back the next day. Having said that, we thought Möhnesee was a highpoint – if only because we saw Barcelona beat Real Madrid in a hotel there that had no German wine!
I could insert some guff here about Germans being exceedingly helpful, friendly, chatty and patient folks but you're probably waiting for some news. Currywurst start at €2.20 mit brötchen and half a litre of beer costs about €3 in a bar or 80 cents in a supermarket.