Chest muscles are often the priority of many strength training practitioners, along with arms and abdominals. It is true that these muscles are aesthetically important, but too pronounced a development can lead to deforming the bust.
The reason that wants this in general and related to a lack of strength between the agonist muscles (Pectoral) and the antagonist muscles (dorsal), is for this reason that we meet people with prominent pectoral muscles and shoulders that go forward.
For others, this muscle group can be very difficult to build. If you have difficulty taking pectoral muscles with basic exercises such as the bench press or dips, isolation work on the machines or with a pulley should be considered.
You will also have to put your ego aside, because often practitioners try to lift far too heavy loads with an awful technique. This is to the detriment of the development of this muscle group.
Concerning stretching, their interests are often discussed and debated. From my own experience and observation, I think it is in your interest to stretch, for a good reason… Avoid increasing your muscle stiffness, which results in undeniable losses of mobility over time. This can become a real handicap.