I'm also very sensitive to my "rear view." Soma makes a bra that is designed to minimize back fat (only, in my case, it does nothing at all good for my front!) and I think that the Spanx brand bras are supposed to be good about this also. I have found that this is just another area to check about how a bra fits. Some bras are much worse in creating this than others. There is also the possibility that a bra isn't capturing all the breast tissue on the side of your body, and this is being displaced as "back fat" when it is actually something that belongs elsewhere.
In terms of clothing, it all seems to go back to cut, fit and fabrication. Some things stick, some things skim. I have found that slight-A line tank tops and tees work pretty well. I have several tops that are actually woven, but cut like a tee, and wovens don't cling as much as knits, so this is helpful to me. For winter, a woven shirt under a sweater makes a huge difference, and in summer, I look for sleeveless woven tops to wear under pullover sweaters later on. I'm not sensitive to itchy knits, I live in a mild climate, and I find that sleeveless tops work well under blazers as well.
I have also found that certain structured dresses, if the fit is right, can be very flattering. For instance, if the dress is designed so that the waist is emphasized with fabric pieced together and sewn, that seems to be better than something like a princess seamed dress where there is continuous fabric.
Another thing to look for is bottoms that are higher in the waist with friendly waistbands. There seems to be a cascade effect with a bottom that creates a muffin, and the muffin seems to rise causing the rolls to appear to multiply When I have on a bottom that comes up higher with a waistband that doesn't bite, the bra fat issues is also helped. Some people are helped by tops with side shirring, but I have found that due to my short torso, it isn't usually in the right place for me. I do have a very casual tee shirt that is magic in this respect, so keep trying. And, dolman sleeve tees are very, very helpful, because there is extra fabric just where it is needed. I have a black 3/4 sleeve top, and also a sweater with this design, and they are both magical in their flattery.
Another tip: have the sales clerk use your phone to snap a picture of your rear view so you can stand naturally with your arms at your sides. If you lift your arms to take the picture in the mirror over your shoulder, you are largely fixing the problem with your arm position, and you will not get a true image to help you make a choice to minimize this area of your body that you would like to correct with clothing if you can.
