Form my experience the Paragon feels less bulky than the Sheath and also feels less bulky than the Apple silicone believe it or not. YMMV though as people have different perceptions.I'm also debating between Sheath and Paragon (leaning towards the Paragon.)
Funny enough, I had a Spigen Liquid Air for my old 13PM. It's way lighter than my temporary case but I don't really notice it weight-wise as much as I notice how less bulky it is while holding it. For the price you can't go wrong with it but when I first got it the back felt "dry" but eventually it became it became oily. (with heavy use) The drop protection was surprisingly decent, my old phone has no scratches just a little dust.
Do you think your old Sheath is bulky? More than anything, I'm hoping the Paragon feels less bulky.