From a legal standpoint there is only one real question in this case that matters.
Does the President have absolute de-classification authority and does the act of removing such from the WH, while still President, qualify as declassification.
This was the accepted precedent by the courts after the Clinton tapes case brought by Judicial Watch (and decided by a Judge now on SCOTUS). Her opinion was clear and nobody appealed it (of course) so it is the best indication we have of the Federally accepted “opinion” on the law.
All of this noise you hear on the left or the right about “the nuanced issues” surrounding the case are just 24/7 news-babble and rank partisanship. SCOTUS tends to condense cases down to single issues and if there is prior precedent within Federal courts it is quite rare for them to turn that upside down (even liberal justices don’t often do this).
There is little doubt that every prior President removed “documents” from office when they left, but what matters is the law and rendered opinions about the law. I believe the Justice called the authority “absolute” or something similar.
Yet Joe Biden removed reams and reams of documents that he had no authority to possess as VP and nothing is done about that by our completely compromised, corrupt and illegitimate DOJ.