What are the difference between Vestibular stenosis/ functional rhinoplasty and a septoplasty?

Hello, it may be helpful to think of the nose as two separate but related parts. There is the breathing/function portion and the outward/external portion. The external portions (ie the appearance of your nose) can be changed without necessarily changing the breathing portion, and vice versa. Additionally both the appearance of the nose and the function of the nose can be altered at the same time in the same procedure.  If both issues are being addressed, it often requires some surgery on the septum (aka septoplasty) and then alterations to the outward appearance of the nose which can include reshaping the tip cartilages.  I would recommend asking the surgeon specifically what portions of the nose he/she will be addressing and what the intended goals are with each respective portion. Hope that helps and good luck. 

Great Question!  A septoplasty can be done by an ENT or a plastic surgeon.  They take the crooked cartilage out, which often helps open the nose and helps the patient breathe better.  For some people this is all they need.  A septoplasty is a surgery for breathing and does not affect how the nose looks at all. 
Repair of vestibular stenosis is actually a cpt code that is billed in a functional rhinoplasty.  A functional rhinoplasty is a "nose job" that is done with the primary goal of improving breathing.  While a well done functional rhinoplasty should also look good, the goal (for insurance) is breathing, not looks.  We differentiate this from a cosmetic rhinoplasty, which is where the patient breathes fine but wants it to look different.  I would argue that any rhinoplasty done well should look great AND help you breathe better.   The difference is drawn mostly for insurance.   
The repair of vestibular stenosis is a code for putting in spreader grafts.  These are little cartilage grafts that work like "internal breathe right" strips.  For some people who have valve collapse in addition to a deviated septum, both procedures are needed.
The way to find out what you need is to visit a facial plastic surgeon.  This is a doctor who trained in ENT but also in facial plastic surgery, so they are expert in form and function of the nose!  A thorough evaluation and looking in the nose with a camera (endoscopy) will tell what you need.
Best of luck
Dr Rodman