Relational data modeling for sub types

Question

I am learning the Relational Model and data modeling.
And I have some confusion in my mind regarding sub types.

I know that data modeling is an iterative process and

Answer 1

I like Fowler's treatment of Class Table Inheritance and Single Table Inheritance. You have touched on both of these designs here. Each of them has its uses and its drawbacks. You can use these as search terms and you'll get a lot to read. Some of it is worthwhile. There are even a couple of tags here in SO with those names.

I'm not sure about today, but subtypes were often omitted from Database 101 courses back some 20 years ago, and it was something that every database builder ran into as soon as they got into "the real world".