I called today but the person in charge (kleines Rathaus) was in a meeting and has not yet responded to my email regarding this. But I would for now assume that something similar to the eaves height is meant, as otherwise gable roofs would only produce glorified attics.
The basement is currently quite uncertain, as there is some slope but presumably only so little that it can still be excavated to a reasonable price. Without a basement, however, it definitely means a larger attic and thus a steeper roof. From a smaller apartment, one also has quite a few things that are only needed occasionally, and storage rooms on the ground floor are definitely out if one plans with a study and a technical room.
We also gave some thought to the orientation. An east entrance would offer short distances, but only makes sense if the entrance is on the long side, otherwise the hallway becomes quite tube-like. However, then the gables would be north and south, which we do not currently like for several reasons. First, we feel we would be giving up some of the sunny side. Second, the southwest terrace would then be much further south at the neighbor’s, since we do not yet know how they will build, we assume they will also tend to position more to the northeast to get sun from the south. And the third point, I am still somewhat uncertain about its extent and relevance, would be the photovoltaic system which would significantly shadow itself with a steep east-west roof (see attic). Currently, the idea is rather to place the entrance fairly centrally on the north side and rotate the house slightly so that it faces exactly south. The technical room then maybe northeast and the study northwest (view of the garden).