these days, i’m pretty sure you can use the properties of the carbon layup to create almost whatever amount of compliance, flex, stiffness you want with dropped or traditional seat stays. so while optimizing aero properties undoubtedly affects stiffness (the elongated / boxy shapes that are aero are also stiffer in one axis than another, etc) a good design process can optimize both - or choose not to.

i have two carbon road bikes at the moment, and the one with traditional/undropped seat stays (s works aethos) is a much smoother, lighter ride than the one with dropped stays. sloping top tube also helps, i’m sure, but again, could almost certainly be cancelled out by the carbon design.

my preference, based entirely on aesthetics and my personal experience, is for a slightly sloping top tube, undropped stays, and slightly tapered slightly elliptical tubes. not the most aero thing, but light and beautiful. like the cervelo at bottom right of your roundup.