The Gospels essentially copy paste chunks from each other
Luke copies from Matthew, that’s it. Luke also admits he’s pulling from other sources in the prologue. Modern scholars add a lot of speculation and try to make a scandal out of this, but there’s really nothing to it.
There’s no evidence for Q and it was never even accepted by worldwide academia, it only gained traction in pop level books and Jesus Seminar type projects.
pseudo Pauline Epistles
Entirely explained by dictation, which we know happened, because some of the epistles reference being dictated.
There was a lot of reconstruction, editing, etc, going on.
I’m not going to convince you otherwise, but I’ve explained at length why they couldn’t have been significantly edited unless it happened extremely early on. Like, even before the turn of the next century, because they’re referenced by Pope Clement I, and Clement’s first epistle is practically identical in content to a Pauline epistle.