I'm 5'9", 165 lbs, and a 36DD. I typically wear a 8/10 or M/L, and I ordered the L in this suit bottom. I think Inamorata is one of the only brands that actually sizes their suits well. I liked the fit of the L, but I could have also probably fit into the M. (Whereas with countless swim suit brands, I'm needing an XL minimum in bottoms.)
So I think sizing with this style kind of depends on how you like your suits to fit! I sized up and liked it -- super high cut in the leg, super high-waisted (like, actually!), and the quality is great. My only note is the back rides up with any movement. So it's kind of like a constant wedgie. If it had less fabric in the back, it'd be fine as a thong. But I think it could maybe use a touch more so it doesn't ride quite as much. Just a heads up!
Rated 0 on a scale of minus 2 to 2, where minus 2 is Runs Small, 0 is As Expected and 2 is Runs Large