Do you think we could do better than this kind of discussion:
Person A: "There is something about the taste of apples...."
Person B: "What!? Don't you think apples grow on trees?"
lol, I hope we could do better than that level of discussion.
...
Lemme address more directly the complete unknown you asked about --
It doesn't make sense to me personally to guess that God would make a 'copy' of brains. It seems too simple to me personally -- why should God be limited to just 21rst century ideas/speculations we have from our recent science/technology like making a data copy?
(i.e. -- that kind of limitation itself wouldn't make sense; more likely it would be something surprising to us, instead of ordinary)
We could at most only speculate. e.g. (random speculation): Transform the physical by some transformative process somewhat analogous to a chemical reaction or analogous to how a caterpillar in a cocoon transforms into a butterfly, etc. -- e.g. maybe the Quantum Mechanics idea of conservation of information (that information can't be destroyed or created) isn't breakable in a way that is best, so a transformation is best (this is speculation).
Who knows? Any such guessing (I'd expect also including when someone thinks they know) is purely speculative.
But the way spirit is connected to the physical is entirely mystery.
Consider further -- if spirit could be described/tested in some objective way, it would contradict scripture also and all would stop making sense, since any testable evidence would prevent/preclude/obviate 'faith', which is to believe before any proof -- objective evidence would prevent/destroy the central key goal of life here as described by scripture.
So, if scripture is correct (and if I understand this part correctly), then mere proof is always impossible to find, by God's intent that it be impossible to find, and any actual clear simple direct evidence would be proactively removed to help maintain the opportunity for faith.