Comparison of Architect to General Contractor or Turnkey Construction

that one particularly has the advantage of having an independent and detailed construction management

You can get that with every project (except from the developer). Either you pay the architect for it or your expert with the general contractor. So no advantage with the architect house.

Sorry that I am only coming to this now, but in our case, we already have a plan from the architect that we want to implement, i.e. the general contractor has to build individually for us, and I am now considering how to proceed after phase 4. So I wouldn’t be wrong with my assessment, right? I’ll start looking for discussions.

So the main costs with the architect are still to come – or with the general contractor. There are various posts from about the further procedure. In the end, the house will cost more or less the same. With the general contractor, however, you can hardly influence any additional special requests that arise during the construction.

You can get those for every project (except from the developer). Either you pay the architect for it or your expert pays the general contractor. So no advantage with the architect house.

But I would have to pay him again separately....

But I would have to pay for that extra again...

You do anyway – service phase 8 with the architect or expert during construction with general contractor (whereas the expert only causes a fraction of the architect's costs – architect 1/3 of the total bill, since numerous trades must also be coordinated and supervised).
Extensive package from the Homeowners' Protection Association (just as an example):

So the cheapest alternative would be phases 1-7 and then the expert, right? But the inspection would not be as effective because the expert has to extensively familiarize himself with the execution planning!? Would that be acceptable?

So the cheapest alternative would be phases 1-7 and then an expert, right?

Cheap yes, sensible no. Phase 8 is more than just supervision: If you trust yourself technically and time-wise with the most difficult part of an architect's tasks and only need a third party to check the quality, then you can do it that way. So construction management, invoice checks, etc.

But the supervision wouldn't be that effective, because the expert has to painstakingly familiarize themselves with the execution planning!? Would that be acceptable?

For me a no-go - see above.