Been a long time since I looked at this, as I got so irritated with things like this, I just started putting nodes into IwBpLib, to get what was needed.
But,
It looks like, you will wish to use something along these lines.
BoxOverlapActors, should be able to give you all actors that are overlapping (even though you should already have that from the OverLap Begin, but if you do subsequent queries, this could be useful)
Now once you have the actor, use
Get Root Component (it will be a scene component coming back, but that’s fine).
Then
Get Component Bounds, now this is where you get the “extents” in the 3 dimensions of the “box” enclosing the actor, and then can do the compares to see if one box, is enclosed by another.