Blueprint inheritance works just like C++ inheritance, in that you will have the member variables of your parents, but not of some random other class. If you want a class to have a property Width, then that class, or one of its superclasses, must declare a property Width.
If you want to configure a few independent things together, make them components, and add them to the same actor, you will then be able to configure values for the different components when editing that actor.