The only part I can answer is the what is affected by Family Catagory (Since I am an Architect). This affects what default parameters might appear in the family. A door has a different set of default reference planes, parameters, etc. in it, than does a Generic Family, or a specialty equipment family. Also, some catagories of families can be cut in section, and others cannot. They'll always show in elevation, no matter what you do. That is why you sometimes need to nest a Generic Family within a specialty equipment family. Generic families will be cut, and Specialy Equipment cannot. By nesting, the generic will be cut within the Specialty equipment catagory, thus achieving the behavior you want.
