I chose this as an example, because the outfit comes with multiple parts. I’m using “ TheKite’s Handmaiden” by Niero and TheKite for an example outfit. Caliente’s Beautiful Body Enhancer -CBBE- by Caliente and Ousnius.
Why does an outfit need breast physics? So women dressed in cotton blouses aren’t mistaken for robots, or worse, synths!
This guide shows the cloth-physics method to obtain breast physics on a CBBE outfit using Outfit Studio for Fallout 4.