Just by looking at pictures, because obviously you can’t measure me, would you suggest UHP or HP breast implants? (photos)

For a more natural, yet still very round shape, the HP would be a better choice.  The UHP would give a more unnaturally round shape.  If you go to your PS's office, you may be able to try on samples of both styles in different volumes to see which you like best.  That would be a great way for you to see what you would look like afterward.  Best of luck!

I recommend HP.The implant selection should be based on a combination of your desired size, soft tissue dynamics, breast base diameter and skin elasticity.  I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with.   Finally, make sure your surgeon is a Double-Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS), a member of the American Society of Plastic Surgery (ASPS), a member of the American Society of Aesthetic Plastic Surgery (ASAPS), and a fellow of the American College of Surgeons (FACS).Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach TrainedDouble Board-Certified, Double Fellowship-Trained Beverly Hills Plastic Surgeon

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 a 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). 
In general, the difference between a high and Mod (+), in reality, is very small (on the order of millimeters).  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 (+) profile which is relatively more subtle and understated. That being said the vast majority of patients will select a moderate + profile device (especially those seeking a more natural and subtle result).
I often find it is easier to decide on a profile (rather than a volume), this combined with BWD will determine volume. Trying to match a particular volume to a profile may lead a BWD mismatch. In my practice, smaller framed individuals do prefer higher profile devices. I discourage pursuing significant volume as this is a hallmark of the "augmented" or "fake" look. Small girls typically have smaller breasts. Over-sizing leads to a frame mismatch which is not "natural." The difference between mod (+) profile and high profile is subtle and less dramatic than the difference between low profile and the alternatives. Ultimately, it is a choice between more or less subtlety.
With regards to your specific question, if you are truly seeking a "natural" look I would avoid ultra high profile devices. Anatomy defines cleavage, not implants. No implant choice will correct for widely spaced breasts (that being said, this does not appear to be an issue based on your photos).
As always, discuss your concerns with a board certified plastic surgeon (ABPS).