Will high profile implants look too round and full on my frame? 5’3” and 105 lbs. (Photo)

Hello and thank you for your question. Judging
from your photographs alone, I think you can still achieve your desired full C cup with a moderate profile implant.  From a general standpoint, your question does
bring up the overall process of ideal breast implant selection which can
be quite involved, as breast augmentation involves a number of different
issues.  The first step would be to clearly define your desired
breast outcome goals – this would include the size you would like to achieve,
and your ideal breast shape.  I would then select the best breast implant
for you based on:
(1)   Volume of the implant – actual
implant sizers that you try on during your consultation can help with
this.  I commonly used the Mentor volume sizing system for this purpose. In
general, 150-200cc is necessary for an increase in a single cup size.
(2)   Contents of the implant –
saline vs silicone, saline tends to be a little stiffer, rounder and can cause
rippling of the skin
(3)   Shape of the implant – round
or anatomic; I would show you how both round and anatomic can provide a natural
shape.  Different profiles of an implant would
also affect the projection of your breast.
(4)   Position of the implant – if
it is over or under the pectoralis muscle; each location would provide a
different shape and projection.  The advantage of going “under the muscle”
is that it provides a lower risk of capsular contracture, lower risk of skin
rippling, and better visualization on future mammograms.  Also, many
patients describe the appearance as more natural, and describe the feel as more
consistent with that natural breast.
(5)   Skin stretch of your breast –
younger patients tend to have more taught skin with more… SHOW MORE resilience,
and respond well to an implant; compared to an older breast with more stretch
marks, which would typically requiring a larger volume to fill the breast
(6)   Degree of breast ptosis
(sagging) – a significant sag would benefit from a breast lift
(7)   Breast diameter and overall
chest circumference
(8)   Native breast tissue volume –
the amount and distribution of the natural breast tissue.
(9)   Any history of prior surgery
or trauma to the breast
The next step for you is to seek out a
board certified plastic surgeon who specializes in aesthetic plastic
surgery.  In your consultation, be sure your surgeon addresses all your
concerns and discusses the surgery details including the position and size of
the incision used (with actual photographs), the type of breast implants
available, the risks and benefits of the procedure, recovery time, and
post-operative course.  Also, be sure to see plenty of before-and-after
pictures in women who have a similar breast appearance to yours, and preferably
at different time frames (3 weeks out, 3 months out, etc) to more accurately
predict your own surgical outcome.
And lastly, I think the most important
component of the consultation is to establish a good connection with your
plastic surgeon.  It’s the connection that allows you to clearly define
your desired breast outcome goals, the first step of this whole process. If you
don’t feel you have a good connection with your plastic surgeon after your
consultation, he/she may not be the best surgeon for you.
For more information on breast augmentation,
please refer to the link below.
Good luck.
Mark K Markarian, MD, MSPH
Harvard-trained Board Certified Aesthetic
Plastic Surgeon

Profile terminology will vary from one manufacturer to the next. The terminology matters less than the correlate dimensional measures.
As one goes up in profile the footprint or BWD of the device will shrink and the projection will increase for a given volume. I have found that full profile Allergan implants correlate closely with high profile Mentor implants. These devices exhibit higher projection than similarly sized moderate (+)/moderate profile devices. Ultra high profile is simply the next step upwards in projection.
Patients are encouraged to stay within the boundaries defined by their BWD. This is the best way to avoid the dreaded "fake" look. I generally recommend that patients with smaller frames who are seeking more than a modest augmentation consider a higher profile device.The higher profile device will impart greater projection and thus a less subtle result but will allow for a more significant augmentation than a similarly sized Mod/Mod+. Thus, the ultimate question is one of volume. Is the volume you can achieve via a similarly sized Mod + profile implant adequate to reach your desired goals? If not, a HP will afford you more volume at the cost of subtlety.
The difference between higher and lower profiles for a given volume is projection and for a given width is volume (with the high profile implant being greater in both scenarios). The moderate plus is the most commonly used profile in my practice. It allows for the most reasonable volume in given BWD. In my practice, low profile implants are the least commonly used (widest and flattest). I will typically reserve high profile devices for smaller framed individuals or those seeking a less subtle more dramatic change (the opposite of natural). 
Smaller framed patients tend to prefer HP implants as their BWD can be restrictive with regards to volume. An HP implant will provide greater volume in the same BWD footprint. But remember "natural" while difficult to define often implies a good match between frame, volume and projection. If the goal is natural more conservative sizing/volumes are recommended.
In general, the difference between a moderate and Mod (+), in reality, is very small (on the order of millimeters). Anecdotally, most feel that moderate profile devices are too flat. In my practice, I generally classify profile based upon patient preference. A higher profile provides a more dramatic look (size for size) vs. a moderate/moderate + profile which is relatively more subtle and understated. That being said the vast majority of patients will select a moderate + profile device.Based upon your photos, unless you are willing to accept a more subtle upsize, a higher profile implant is recommended. A moderate (+) profile device will likely not deliver the volume you are seeking (but it remains an option).
As always, discuss your concerns with a board certified plastic surgeon (ABPS).