Dear Claire,
There are several aspects to your question that must be considered. You are clearly a small person so you don't want implants that are too big, making you look unnatural and even, potentially, freakish. Most of my patients do not want to be "showy" but they want to see a difference, in and out of clothes.
After 20 years of practice, I know of no way to pre-size patients accurately in advance of surgery. Simply stuffing implants into a bra tells you nothing about what they will do for you in your breasts- the situations are not comparable. Computer programs cannot take into account the many variable found from one patient to the next in terms of skin elasticity, breast tissue quality, and more. I have found that using breast sizers intraoperatively works best. These are reusable, adjustable breast implants that can be inserted into each breast once the preparation of the implant "pockets" is completed. The sizers can be filled to whatever size desired to see how the breasts look and feel with an implant in them. Some judgement is necessary to be able to visualize the results months down the road. This requires that patients communicate their desires clearly to their surgeon and trust that the surgeon will follow this to the best of his or her ability. Surgeons must also clearly explain the limitations of the surgery.
There is no standard for what an A, B, C, or D cup is. Each manufacturer makes bras according to their own standards and these vary greatly. Using cup size alone as a measure of the surgery is a set up for disappointment. A natural, well proportioned appearance with minimal risks of problems should be the ideal. The best size implant will be greatly determined by what each patient brings to the operating table, literally. I have found that when patients choose their own implant size, they are often disappointed, and usually by choosing too small.
The issue of implant style is interesting and I feel that too much is made of it. The majority of implants used in the U.S. now are round, smooth, moderate profile implants because these produce the best results in most women with the fewest problems. High profile implants are useful in patients with narrow chests who need or desire more projection with smaller volumes. I rarely use any other style of implant. I do not like the textured or anatomically shaped implants (also called "tear drop" shaped). They have too many problems that I do not want to deal with.
I hope you are successful in achieving your goals. Don't be afraid to ask a lot of question, ask your surgeon to explain his or her recommendations, and, if necessary, seek another opinion.
Sincerely,