It requires you have a primary key. That's it.

Everything else table names, fk's, multiple databases, etc. is overridable. The only thing I know of that is a slight headache is postgresql namespaces (aka schemas).

Django does make choices for you. But almost everyone of those choices can be overridden. I have found that most people who think Django (or any large/mature/widely used project) can't to something is because they don't know it well enough.