Thank you very much in advance for the answers.
Unfortunately, it was not possible to do it differently with the various developers, since this is a new development area and the plots were sold individually by the municipality.
It is to be built two stories with an attic studio with SD. It should already be an energy-saving house. We also want triple glazing, but this will probably cost us a small extra charge, which is clear to us. There will probably also be additional costs for the front door and bathroom because the standard simply does not correspond to what we want. It's all a matter of money.
We are already trying to get a bill of quantities from the developer so that we can have an offer prepared by our friendly craftsmen. Unfortunately, he is not very cooperative in this because we have not yet signed the contract for work. But once we have signed it, I don’t know if he will then accommodate me and remove it from the contract and credit us if our craftsmen are cheaper.
Then the point about financing is already good, that we have not yet signed a contract for work for so long might possibly still allow us to change the developer.