The logical hierarchy based on the building categories is Geographical area -> Site(s) -> Building(s). Buildings with the same category can also have a hierarchy. For example Building -> Sub building(s). The categories do not impact the use of parent/sub buildings. Technically it is possible to have a deviating hierarchy like Building -> Geographical area(s), but this is not advised because this can lead to issues when using Workplace Experience.
Next to Workplace Experience, also other integrations can have specific rules for the building hierarchy. So it is advised to used use the recommended logical hierarchy of the categories.

A logical hierarchy based on the area categories is Main area -> Floor(s) -> Meeting room(s) / Workplace(s) / Parking places. It is possible to add another level in the hierarchy between the Floor and the Meeting room / Workplace(s) / Parking places to combine several areas or if it is a specific room with multiple workplaces for example. This extra level can be added with the 'Area (general)' category.
Technically it is possible to have a deviating hierarchy like Main area -> Workplace -> Meeting room or a hierarchy where the same category is used multiple times, but this is not advised because this will lead to issues when also using Workplace Experience.