Yes, all cabinets can be used as the Main cabinet but auxiliary cabinets can not be connected to all mains. I.e, if you want to use a DC100 as an auxiliary cabinet the main cabinet will need to be a DC100 also. This is because the controller needed for handling DC100 cabinets only exists in the Main DC100.
The pictures below show the different ways cabinets can be connected. Please note that the first AC100 cabinet always needs an interface box and the following AC100 will be connected to that interface box.