BA: moderate profile 275cc o 295cc? Is it too big, I don't want that huge stuck on boob look. (Photos)

Hello and thank you for your question. You are a great candidate
for a breast augmentation.  275cc or 295cc should be able to accomplish your goals.  The size, profile, and shape of the
implant is based on your desired breast size/shape, your chest wall
measurements, and soft tissue quality.  This decision should
be based on a detailed discussion with equal input from both you
and your surgeon.  This entire surgery
can be performed with a small incision technique.  Make sure you
specifically look at before and after pictures of real patients who have
had this surgery performed by your surgeon and evaluate their results.   The most important aspect is to find a
surgeon you are comfortable with. I recommend that you seek consultation with a
qualified board-certified plastic surgeon who can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D. FACS
Harvard-trained plastic surgeon

Choosing the right breast implant size is of course a really important part of your consultation. To get this right means you'll be happy with the result and comfortable with your decision!
There are many factors that come into implant choice but the ones that impact the volume or size relate to what look you are after, what your chest dimensions are and how much breast you have already.
There are a few techniques that help you and your surgeon decide on size. The more sophisticated techniques are the use of 3D photographs of your chest with the Vectra which can be used to simulated different implant sizes so you can get an idea of the look. I also frequently use implant trial sizers which are soft shaped silicone inserts that can be put inside a non-padded bra to get an idea of how the size feels on your chest because it's not just about volume but also the weight of the implant. 
The other less sophisticated but useful test is the rice test. Using a measuring jug with an inscribed mL measure on the side, measure out 250mL (roughly equivalent to 250cc) of rice and pour into the toe of a sheer stocking. Tie it off so that its not too tight and cut it close to the knot. It should be loose enough that if sitting on a table it flattens out and is fairly pliable. This can then be put into a bra that has no padding at all. It can have an underwire but the best are the really sheer, thin fabric ones. Wear a T-shirt over the top for a while to get a felling for the look. Add no less than 50cc at a time to increase the volume. Sounds like a project and a half but it's a good test to do at home in comfortable surroundings, when you've got plenty of time.
You have a really nice breast shape, and I think that the size implants you are considering will give you a lovely result!