Breast augmentation is enhancement of the natural appearance and shape of the breast. The variation in chest shape, breast shape and size, can be considerable and you can begin to appreciate the differences after viewing many breast augmentation results on the web.
Some chests are broad, and some breasts will have a wider distance between the nipples with less cleavage. In order for augmentation to appear natural, the implant must fit and contour the natural breast, hand in glove if you will.
The implant should be centered on the nipple, and contour well with the diameter and fold of the breast. This may mean that the breast is still more widely spaced that 'ideal' though again the implant must work with and not against the natural breast. Chest and breast shape do influence the breast implant selected.
For example is the implant base is too narrow as in a high profile implant, the gap or separation between the breasts will become accentuated. The placement of the implant can also be affected, say in a wider chest, an under the chest muscle approach may also push the implant to the side and emphasise the separation.
There are limits as each is unique, though a careful consideration of your unique shape can help you plan for the best result possible.
Best of luck.