Poser uses morphs for each body part. The seams however may be identicle and are welded. For morphs crossing body part boundaries you can link the morphs so altering one changes the other , or create a FBM, full body morph which does the same sort of thing. i.e one control dial that alters many parts.

The joint zones control the mesh deformation during joint movement.

and yes, Poser will do smoothing.