Why do my neighbour and I have completely different settings on the airhandling unit?

Airhandling units can have different settings for many reasons. This depends, among other things, on the type of unit, the size of the home, how the ventilation ducts are installed, the floor plan, and how the system has been designed and balanced. The settings are adapted to each individual home and are intended to meet the specific ventilation needs there. Therefore, it is completely normal for settings to vary from one home to another, even if the houses appear similar.