Obtain comparable offers - on what basis?

We have a plot of land in prospect through an allocation system of our city. Specifically, this means we are basically just waiting until all the plots have been distributed (we have already been able to choose our desired plot), and then proceed to the notary.

We have also already approached some prefabricated house manufacturers. I believe there is no need to discuss the behavior of the general contractors any further here. Almost everyone wanted to push us into a preliminary contract, told us that this or that discount no longer really exists, but that it would kindly still be granted to us for 2 weeks, etc. One even wanted to sell us an input plan (on what basis, I wonder?).

In order not to burden ourselves further with these informative but not really helpful conversations, we would like to ask the general contractors for concrete offers. However, the standard house types are hardly comparable. Therefore, the question to the group:

On what basis can comparable offers be obtained?

Should one specifically commission an architect here to carry out a preliminary assessment, preliminary design, or even a design planning? How will this architect calculate the costs for the project, on the basis of which he will then invoice according to HOAI?
Do freelance architects even have an interest in going through only these steps with someone?

I would appreciate some answers; we are currently a bit at our wit's end.

If these questions have already been answered, then please excuse me. I have found nothing through searching.

Specifically comparable is done with an LV, which the architect prepares after the planning. Otherwise, try to compare GU offers and the confusing descriptions.

As Lumpi writes, an architect can create a detailed tender/BOQ and thus the costs can be compared. However, this falls into phase 6 of the HOAI and by then practically everything except the construction itself has already taken place.

The architect calculates his fee for the stages you mentioned based on a more or less accurate cost estimate. This can be detailed by trades or somewhat more general, depending on the architect (experience of your own architect plus testimonials).

I would argue that if you want to build a prefab house or work with a general contractor, an architect doesn’t make sense or save money.

Comparisons of house types then only work roughly via size / floor plan / level of equipment.

Comparisons of house types can only be roughly made based on size / floor plan / level of equipment.

With the detached house builder, it's actually about much, much more:

slab foundation yes/no, batter board yes/no, surveyor, site setup, construction power, construction water, crane rental, porta potty...

Base slab yes/no, batter boards yes/no, surveyor, site setup, construction power, construction water, crane rental, porta potty...

These are incidental construction costs and must be paid by the client. For a solid house, the base slab is included; for the prefabricated house, the price usually counts as OK base slab. Nevertheless, they offer it as an exclusive service.

Dear OP: The architect will charge according to HOAI. No matter how much you later have to pay a general contractor.

You can compare by indicating sqm, the energy saving ordinance, i.e. KfW70 or 55, possibly already the desired heating system, and some must-haves like, for example, Frisian house, city villa with bay window, 125 mm sand-lime brick with gable roof, average number of windows, colored windows, average standard, clinker. Since you should set a limit on the companies you inquire to, e.g. 3 - 5 (although I find 5 already too many), which have established themselves to give a competent, confident as well as honest impression, the radical comparison of the construction service description should be "relatively simple". However, you certainly cannot compare all services 1:1, but you can weigh them and prioritize for yourself. If, for example, a company includes a drying heater in the bathroom, but you do not want it, you should not place too much importance on this €300 (ridiculous amount).

A first step is the comparison of the construction and performance descriptions.

Furthermore, all providers seem relatively similar based on our experience. The additional costs for extra equipment also roughly even out. For one, the tinted windows were more expensive, but the chimney was cheaper; for the next, it was the other way around, and so on.

In the end, we had a range in which all offers moved. Narrower than expected. Local solid builders were rather at the lower to middle end. That is what it turned out to be.

The cheapest among the solid builders was Town& Country, among the prefabricated houses Allkauf Haus (in our case). Each adjusted for equipment. But not so much cheaper as one might think at first glance. The rule of thumb with at least 2000€/sqm living space fit quite well for us. Now we have even stayed a bit below that.