Presidential papers belong to the “people” — maintained by the National Archives.
The “declassified” narrative is nonsense. Typical Trump false narrative being fed to his moron base because he is aware that more serious criminal statutes come into play with classified material.
But, under any scenario, removing President papers violates the law. Imagine a departing President loading White House furniture, computers, and paintings into moving vans and leaving the incoming President with a vacant empty house. That would be theft.