That's one of the selection in the plugin I menioned in the post. But after messing around with it a bit more, it doesn't really solve the problem as well as I want it to be so I move on the method mentioned in my last post which is the best solution I can find so far.
So I decide to try fixing the armpit areas as well as do some minor smoothening. The armpit looks slightly better now.
I also highly recommend to use the following morph by Kemenate to help better the armpit areas more
https://hub.virtamate.com/resources/morphs-unisex.213/
So I have another little morph for our boys. This time focusing on giving them a fuller and more 'meaty' chest.
This morph is supposed to be used in place of the in game "Pectorials Diameter" & "Pectorials Heavy" morph when you want to enlarge the chest. But feel free to also use them together...