should I offer soother/pacifier to my newborn? As he always open his mouth widely even he is full.

This is more towards personal preference. Some mummies says that it will affect the growth of the teeth. I have given both my boys pacifier since they are born when in the hospital. My elder one teeth grow fine. I feel that it is more to generic than using the pacifier. I have friends reject giving pacifier to their child due to this reason and most of them are sucking their thumb. That will be harder to "wean" off than a pacifier.