Will rhythmic breathing exercises everyday for 15-20 minutes help me with increasing my lungs capacity/size? to further assist me with my daily running?

No science here: Lung capacity / size increases some in marathon runners because of the extra extreme exertion changing the chest wall shape. There's no magic in rhythmic breathing -- i've seen only pseudoscience here. Unless you have asthma, it's your heart and not your lungs that limits your running capacity. Did you ever hear of real olympic or pro-team coaches incorporating this stuff?