Ventilation through wall or ceiling outlets?

We are currently planning the controlled residential ventilation. On the upper floor, our builder is only installing wall outlets for the controlled residential ventilation and is somewhat reluctant to place openings in the ceiling. He justifies this by saying that each ceiling opening would mean piercing the vapor barrier twice, and that each angle in the ceiling is supposed to cause higher noise levels. Is that true? We actually prefer ceiling outlets since the wall inlets would otherwise have to be placed on the only wall where a wardrobe could be set up. The attic is being converted for us, meaning the ceiling is not part of the thermal envelope to the outside. Is the vapor barrier still important in that case?

Furthermore, the wall inlets are generally planned quite close to the door (partly behind the door). Is that reasonable? When the bathroom is ventilated by extraction, fresh air seems to immediately leave the room towards the bathroom.

No, it is not sensible to plan openings on the door... we had to do that in one room because it was not possible otherwise since we also have a visible roof truss, but if it is not necessary, you do not do it exactly for the reasons you mentioned. In our case, the system was planned by the manufacturer based on the floor plan.

If your ceiling is still being suspended under the rafters, the cables may possibly fit in there and share the space with electrical cables, etc. However, this depends on the actual height of the intermediate space.
In our case, the setup was as follows: rafters/battens/foil/aluminum profiles/plasterboards.
We have our outlets for the upper floor exhaust air in the wall and supply air from the floor.

If still possible, have round cables installed and not these flat ones (for example, the flat ones cost three times the price of a round one). However, this depends on the build-up height of the floor, possibly.

I planned and installed our controlled residential ventilation as a DIY project and am not yet finally finished. Therefore, I had quite a free hand regarding the topic.

if the pipes for ceiling outlets were then located outside the thermal envelope, that would be a real problem (condensate) In order to be able to make suggestions at all, information about wall and ceiling structure would be important as well as basically further information about the building.

So for me, the pipes of the upper floor are located between the vapor barrier and the drywall, so within the thermal envelope. Those for the ground floor are in the floor structure of the upper floor. It would have been better, of course, in the intermediate ceiling (less floor build-up necessary, but my general contractor did not agree because the structural engineering was already completed at the time of the ventilation planning).

For me, the spiral duct pipes are outside the thermal envelope, for which I have lovingly covered them with aluminum-coated mineral wool or Kaiflex ;) More effort but runs without problems.