This is about the best image i could find for showing how varifocals ‘good’area of vision can vary by lens, the multi poing focal mentioned above……..all vari’s have it hence the vari, the trick is one having them set up properly and 2 using them correctly.
I’m fortunate I dont need a vari as yet but have access to pretty much any lens I want, for me it would be an Essilor Physio
Re the thickness for a shortsighted person there is a british standard for the mimimum thickness of a lens center, the motr important is the edge thickness