20-year-old with triangular shaped breasts. Are they tuberous and would an augmentation help? (photo)

You have a mild form of tuberous breast deformity.  Correctly done breast augmentation with some internal releases of tissues of the breast will produce a wonderful outcome if you want larger breasts too.  Choose your board certified plastic surgeon carefully and insist on seeing a few outcomes of previously treated tuberous breast patients.  Best Wishes!!

Far more important than the technique is the skill and experience of your plastic surgeon. Choose your surgeon rather than the technique and let them explain why one technique may be better than another.  See the below link on some suggestions on finding the most qualified Plastic Surgeon for a Breast Augmentation.  Always insist on a board certified plastic surgeon.

There is a large variation in tuberous breasts. You have some of the characteristics such as a narrow base width, I don't believe your areola are excessively large. .  I think you have nicely shaped breasts and would do well with a simple augmentation.  The implant will expand your base width and fill the space a little between your breasts.