with the sort of projects i work on, Narrative Drama, we are increasingly using VFX to help us with invisible editorial effects.
mostly these are simple split screens with some offset on one side.
for instance, person A is talking, person B does something unwanted, like move their head away, near the end of the shot.
simple: just run person B backwards from just before the head turn.
this is a very simple instance.
we also play with timing between person A and person B
more complex would be using person A from one take, and person B from another.
we remove unwanted elements from shots, and this can even include another character!
they are all fairly simple masking and tracking jobs.
nick