Wallpaper or plaster? Which is better in new construction?

We want to do the walls ourselves in the upper floor and attic to save costs. .... to be carried out by laymen without prior knowledge

Think it over carefully... I wouldn’t take on large-scale painting work except for simple painting. When I think about the work in our house, it’s real hard labor... and as a layman without experience, you probably need 3 to 10 times the amount of time – at least I do ;)

You first have to have the 15-20,000 EUR to have everything built up by the painter on Q3 with fleece and then painted.

Always remember:
Painter's fleece is organic, adhesive too. Dispersion paint as well. And it makes the wall more or less airtight.

Not so optimal for the room climate.

... Because actually, the house should settle evenly. Because only differential settlement ultimately causes damage to the house.
So if settlement-related damages appear, something was not considered or one of the trades botched the job.

That is the crux of the matter. I don’t understand the effort to want to treat the symptoms. With well-thought-out planning and sufficient statics, nothing should crack in the new building except for a few acrylic joints. I know from years of work as an installer in this industry that drywall is very susceptible to this. When mesh tape at panel joints is forgotten or joint filler is applied too thickly, this happens frequently. But the idea that entire monolithically built walls crack lengthwise or from top to bottom would make me rather call in an expert than wonder how to best "bridge" the cracks. But maybe I misunderstood something? Perhaps it’s primarily about the appearance/tactility of the interior walls?!

btw:
For those who want to take the topic to the extreme, I recommend reading the following: "The Lime Plaster Lie" or searching for it on the "www".

Who is speaking there? The installer? Or the civil engineer?

Can't you just replace the damaged strip of painter's fleece that has cracks? So remove the old one, then close the cracks, and then put new fleece over it

I thought so too, and that was one reason for choosing it. But whether replacing a single strip precisely like that works in practice, I don't know. But: The painter glued my fleece down, so nothing can be removed. That's why I can only sand it off and then the whole wall has to be done.

Painter's fleece is organic, adhesive too. Emulsion paint as well. And it makes the wall more or less airtight.

Is the bare brick a climate membrane then? :)