"3D Coat: how good is its capacity to auto-generate a hollow model with just the right wall thickness?"

Very simple with 3D Coat. In fact I would suppose voxels are the absolute best for complicated shelling as the voxel unit is so small and offsetting it mathematically is fairly simple (I believe). In any case, I've never seen any problems with even the most complicated shelling offsets...positive or negative.

It's one reason why I use 3D Coat for complex 3D Printing of models.