O.k. sometimes it goes also at Lake Constance a little big uphill, if you going with the bicycle at Lake Constanze. Also if you ride around the lake the way go sometimes a little big away from the lake to the hills around.
Anyhow: An alpline-stage you haven't to do. Normally the tours going on asphaltic roads. Some tours have gravelled ways. With a good touring bike and enough to drink you are perfect prepared.
The time sheet calculate with a average speed about 15 km/h. If you know that you are slower you must think about this in your calculation.