This sort of thing has been bugging me for months now.
My current unwrap/bake workflow is to apply smoothing groups after done retopologizing/low-res model, unwrap by selecting smoothing group faces and planar map/quick peel them, then bake.
The results work fine (as seen in the images), but I'm aware that this yields more shells, which means more vertex count in engine.
So now I've seen many people model, and then when they unwrap - they unwrap freely and place seams where they would be hidden - then use TexTools to assign those shells their own SG's...
This is ideal - but i feel it isn't accurate or correct and gives crap baking results. I find a problem with this because from what I see, if you unwrap a sharp angled mesh out into one shell - and now textools has given that thing one smoothing group (as seen in the image), wouldn't that look wrong smoothing wise, rather than six seperate shells?
Hope i've explained this clear enough, and apologies for the noob question.