If EntityB inherits from EntityA, must I also make a CDEntityB class that inherits from CDEntityA?

Question

I mean... is that a good idea?

Answer 1

No. Classes and entities are two completely different things. They do not need to mirror each other and in many cases it is a very bad idea.

Entity to class mapping is also not one-to-one so you can have one class that is being used by multiple entities if you so choose.