Unfortunately, the trend of building "without architects" is problematic: because actually, it is sufficient for coordination to have a common planner. In the case of an end-terrace house, the most relevant neighbor for you is your direct adjoining neighbor. Planning together with them makes implementation easier regardless of who then builds.
The realistic ideal constellation would be a common planner for the entire row, and everyone contracts separately. As soon as one is fixed on a general contractor (GU), usually their included "architect" is also involved. Unfortunately, these are mostly just building application draftsmen, where improvisations follow instead of detailed drawings.
You can send the "Riegelgenossen" a link to this thread.