Construction costs are currently skyrocketing

have it done, the kitchen fitter can at most botch something after the rough installation and plastering.
Of course, it's crazy that something like that costs extra.
You also need sewage there.

Normally, the kitchen fitter specifies the plan for electrical and sanitary, then the rough installation is coordinated accordingly.

Would have maybe approached someone 3 months before moving in

Thank you. We don’t have one yet. I also didn’t know that this was so important. Would maybe have approached someone about 3 months before moving in :D That means I should have the rough plan made? Where should what be placed, etc. For the electricity and stuff? We will also need to discuss the electrical planning soon.

In the "standard" controlled residential ventilation does not cool. Unless with a preheating coil that has been converted to cooling. Then be careful with condensate... Controlled residential ventilation usually has heat recovery, so energy stays in the house, unless the summer bypass is active...