To explain a bit why the boob area often looks like the sample image you posted when you expand the character's chest measurement:
Clothing is DAZ is a 3d mesh just the same as the 3d-figure body is a mesh. The way that the clothing is "molded" to the underlying 3d object is that the vertexes of the clothing are "mapped" to the closest vertexes of the character body. Then when the body shape changes, the clothing vertexes are moved proportionally in the same direction/distance as the underlying body vertexes. By doing this the 3d mesh of the clothing is mostly going to stay outside of the body mesh, and avoid "poke through" (there are other things to help as well but they don't matter much here
But now imagine that you get a significant change in position of *some* body vertexes while their close neighbors do not move much as all... for example, a nice sized b-cup boob like on the default genesis body torso: the underboob vertexes are close to the chest vertexes - and then suddenly she gets a huge inflation and has Fcups and those underboobs vertexes are several centimeters down and forward of original position, while the chest vertexes are still in the same place...
Due to the basic algorithm in use to simulate the "tight fitting clothing" all of the clothing 3d points must follow... and now the leather minidress breast area has a clearly unnatural and uncomfortable shape.
If daz or similar programs had a much more sophisticated simulation of the boob-meat, it's weight, flexibility, and both internal and surface elasticity, and then solves that at the same time as the container (dress leather) is also simulated to move and bend and expand just "enough".. then you would get more realistic looking clothing. But that level of complex simulation is waaaaaay out of reach for the Daz developers (and, being honest, even for university level research work). In the real world, it just happens, virtually instantly, because that's how physics works.
