To what extent does physiognomy and posture play a role in breathing / rythmn and speaking fluency?

To what extent does physiognomy and posture play a role in breathing / rythmn and speaking fluency? Did anyone do extensive workouts for posture and core and seen improvements? I've recently gotten back into working out. Granted I'm tall as fuck but I feel the improvements to default posture and more upright shoulder and chest allow for more fluency because I'm not hunched over and therefore generally feel more relaxed. Side note: I had my sinus canals straightened and i got prescribed a drug which completely freed the airways of my sinuses in a way I haven't felt again. I remember this helped tremendously with fluency too -