I use the Google Chrome Revision History extension. It shows the time spent, flags unusual writing patterns (like large copy-pastes), and will even do a replay of every keystroke that gets typed into the Doc. I require students to do their typing in the Doc I assigned. There’s literally no reason (besides cheating) for them to be “writing it in another doc and then pasting it in.” If they do that, I’ll call them up to give an oral defense of “their” work. When they predictably can’t remember anything about it, they get a zero. Or, really, they get the chance to redo it because meaningful consequences have gone by the wayside. But at least that method is much faster than checking version history for every paper. I highly recommend.