Ik ben Nederlander vs Ik ben een Nederlander.

[dutchdutch]

I am confused about using the indefinite article "een" in Dutch.
There is no article when we talk about a profession: "Ik ben student." "Ik ben docent."

How about nationality?
Q. Are these sentences correct, and what are the differences in meaning:
1. "Ik ben Nederlander/Nederlandse."
2. "Ik ben een Nederlander/Nederlandse."

Q. Is it correct to say "Ik ben Nederlandse" (I am a Dutch (female))?

Q. If it is a man, can I then say;
1. "Ik ben Nederlands,"
2. "Ik ben Nederlander," or
3. "Ik ben een Nederlandse man"?

Q. We can also use an adjective, Nederlandse instead of a noun Nederlander/Nederlandse?
Ik ben Nederlandse. (for both man and woman)
Q. Then we do not know if this is by a woman or man?

Q. If there are two Dutch ladies, do you say?;
"We zijn Nederlanders."