If it’s true black voters really broke more like 96-2 in 2020, then black Trump-supporters/black-Republicans are one of the most insanely overrepresented groups in modern American media and culture.
Would this surprise you? Just look around this forum and see how excited everyone is to talk about black Republicans. If they don't exist, it will be necessary to invent them.
In reality I think that both of the suggestions you made are accurate. Black voters who live in overwhelmingly black areas should be more heavily Democratic (similarly, you would expect gay voters who live in heavily gay areas to be more heavily Democratic), which means that the true Democratic percentage of the black vote is probably less Democratic than results in these areas would indicate, but also exit polling (particularly in 2020) should not be trusted. Consider what an exit poll means in theory—polling voters exiting their polling places—and reflect on how this would have worked in 2020.
How much less D do you think black voters are who live in heavily non-black areas?
Imo, in the deep South politics is so racially polarized even blacks who live in 99% white communities likely don't vote much different from blacks in 99% black communities.
Basically anywhere else, it gets more complicated.
I imagine most recent black immigrants likely vote substantially less D than blacks who have lived generations in this Country. What's weird though is in the US, I can't think of a single community that is heavily black immigrants whereas groups like Cubans and Jewish have very clear communities.
Little Haiti? Parts of Flushing?