Noise protection measures according to DIN18005

My question is, however, who ultimately checks whether we comply with the passive requirements from the development plan?

Wrong approach. Regulations are not always meant to hassle the citizen.
Take it as advice to do enough for noise protection. It is hardly possible to change it afterwards. We have already had cases here where people sold the new house after 2 years because it was too loud. Concealing the defect then is difficult.
The same applies to renting. The cold rent is quickly halved if it is proven to be too loud.

Your planner will answer the rest for you.

Take this as advice to do enough for sound insulation.

It usually isn't much more expensive, it just limits the number of options for masonry, windows, and ventilation a bit. And the correct orientation of the rooms in the floor plan is usually free, but probably the most important point. The executing construction company must provide proof. Or are you doing a lot yourself?