You are naturally more symmetrical because you are training your whole body hard. If you take a look at the rugged builds of the old timers, you will notice that they had symmetry. They trained all the major muscle groups hard and heavy with a wide variety of multi-joint exercises, many of which are not commonly done today. We now call them tendons. To build tendon strength, you must lift heavy and pay your dues.
Tendons only get thicker from heavy poundages.
Toning and pumping won't cut it. I honestly believe that the training information for the development of muscular size and strength was better 50 years ago that it is now. You will be amazed at how much they knew and how right they were. They were not afraid to do singles. They enjoyed testing their strength doing a wide assortment of odd lifts.