Ceiling outlets for controlled residential ventilation, is that correct?

Quickly and I'm not a professional:
For nominal ventilation, the controlled residential ventilation should be at about 50% performance, I would definitely take a device one size bigger.

Two valves in the parents' room would be better against noise and draft sensation with the high air volume.

I'm not an expert either

Regarding the system, I also asked whether I should take the bigger one after all; I was told that the one is sufficient and they referred to the calculation.

Regarding the valve in the bedroom, it's basically two ducts running through and at the end it leads to one outlet, is there then a difference?

Is that a closed pantry or a counter in the kitchen? If closed, then place a vent there. Otherwise, maybe also.

At first it is my PC corner, later possibly an open pantry or back kitchen.

No, for each fresh air valve better only up to 30m3/h. 40 is also possible, but you might have more drafts and noise than if two with 20m3 are present. hrad in the bedroom I find important.

Take the device one size larger, otherwise it will struggle, be louder, and possibly consume more.

Initially it is my PC corner, later possibly an open pantry or back kitchen.

Then just put the valve there.

See last paragraph .....was still in the attachment.

Sorry, I wouldn't let any layperson plan this, but rather follow the suggestions of the architect, heating engineer, and planner.