I always thought that you plopped the meringue on the pie, then stuck it back in the oven to ‘cook’ the meringue. Recently I’ve seen more than one blog/show/recipe that uses a kitchen torch to “lightly torch the outside of the meringue til brown.”
How do you not end up with a pile of goo using that method? I can’t imagine a 15-second torching cooks the meringue such that the pie is even sliceable… 
I had a similar experience with the reverse sear technique for steaks and didn’t believe it would get results until I tried it. My suggestion is make two lemon meringues, bake one, torch the other, and see which one turns out better… And save a slice for me.
Depends on what type of meringue you are using. Some meringues are made with hot sugar so the eggs are cooked already and is quite stiff.
That is what I would use for a pie or tart.