Building plans are initially available only digitally

Do you know this procedure? A civil engineer from a construction company creates the building plans for us free of charge. Coordination and discussion take place at his PC. He then prepares an offer for us, which we receive in writing for financing purposes, but not the plan. Otherwise, we could go to the competition... Once the contract is signed, the plan goes to the municipality.

I find it understandable. He provides a service for you free of charge and does not want to make it available to the competition.

A freelance architect might charge you a few euros for the first draft. It varies from company to company.

Also, for example:
Küche1: sorry, we are not allowed to give drawings or written documents outside the company.
Küche2: after the initial consultation, receiving complete documents without request handed over
Kamin: (very nice pictures adapted to our floor plan, with decorations and everything) We only received the pictures after we had verbally agreed to work with them
(besides the colorful pictures also solid price/performance compared to others)

I find it understandable. He provides a service for you free of charge and does not want to make it available to the competition. A freelance architect might possibly charge you a few euros for the first draft. It varies from company to company. Also, for example: Kitchen1: sorry, we are not allowed to give drawings or written documents outside the company. Kitchen2: after the initial consultation, received complete documents without asking. Fireplace: (very nice pictures adapted to our floor plan, with decoration and everything) We only received the pictures after we verbally agreed to work with them (besides the colorful pictures also solid price/performance compared to others)

In general, I also understand the approach. It is just difficult because I don’t know how to compare the offer without a plan.

You can offer to pay for the planning and have it credited upon purchase. It's all good and fair.

It’s just difficult because I don’t know how to compare the offer without a plan.

If by "plan" you mean drawings (floor plans, sections, elevations), they would hardly help you compare: the more decisive basis for comparison is quantities and specifications. A house that looks supposedly the same from pictures will have a completely different price with differing descriptions of construction services. Against tricks to appear cheaper (omitting incidental cost items, vague terms), making drawings for the preparation of requests for offers does not help at all.