The reason you are confused is because many plastic surgeons have minimal experience with M to F transgender patients, or have a tendency to use a certain profile implant with all their patients, female and transgender alike. This is wrong, IMHO.
At 5'8" tall, you would be considered a tall female, but your present chest and breast base anatomy is masculine (relatively wide, with taut skin and youthful robust musculature). Your surgeon and you should first determine the implant size needed to give you the breast volume you wish (that presumably is proportionate to the rest of your body), and once that is determined choose the implant profile that achieves that volume with the best match to your breast base diameter. Depending on size this would likely be moderate profile implants, or with somewhat larger implants, moderate plus profile implants.
This should be considered only when hormone therapy has enlarged your breasts as much as possible (12-18 months after initiation of hormone therapy; most patients will develop no more than about one cup size of breast tissue).
Because M to F transgender patients do have more pectoralis muscle bulk and taut skin than their physiologically-female flat-chested counterparts, anywhere from 1/3 to half of transgender patients will benefit from consideration of tissue expander placement to stretch the lower pole muscles and skin to yield a natural teardrop shape and adequate skin/muscle coverage for appropriately-sized implants. Simply placing implants in every transgender patient unfortunately can yield too-small, firm, convex-up, concave-down shaped breasts with wide cleavage. Totally unnatural look AND feel.
Obviously, it's not just about profile!
Assessment of muscle and skin tightness must be determined before recommending this two-stage surgical approach (or not), but doing this when appropriate will often minimize the need for multiple re-operations to try to obtain adequate size, position, shape, and softness of implants in the transgender chest.
As you can see, one approach and profile does NOT fit all!
There are a few plastic surgeons who perform significant numbers of transgender surgeries, and have office staff, nursing staff, and the associated capabilities that many plastic surgical practices do not have. Seek these practices and surgeons out, and obtain a few more consultations. It will be worth the time, effort, and (saved) expense of an improper choice. As anyone who does do significant numbers of transgender augmentations will tell you, this is NOT simply placing implants as we do in our non-trans female patient! For several examples of my transgender patients click on the web reference link below. Best wishes! Dr. Tholen