Not really I think you are confusing them with western statues, most resin cold cast..etc figures used to be 1/6.>but don't resin figures tends to have more than just a character, which leads to the figure being way more massive than some solo PVC 1/6
Not necessarily but nowadays non-PVC is more related to elaborated bases complex poses and sometimes as you said two characters.
Volks(resin): very good quality & good packaging
New line:Good quality & good packaging
Aizu project: Varies but usually from Good to very good quality & very good packaging
Amie grand: decent sculpt but hideous packaging, a leg came broken plus other parts