My experience with Jupiter has been that seeing that fully supports 250x in an 8, 10 or 20" is revealing a high intermediate level of detail, not what I consider the truly small stuff. The 250x to 275x level of resolution for planetary features is a notch past where my 110ED or 127 Mak top out for example, even when the seeing is much better than that. Things are just starting to get interesting at this point, rather than providing a high water mark for large aperture.
In some of these discussions, I wonder if folks have actually observed many of the smaller details. There is another range that emerges when the seeing settles enough to support 350x and beyond. The 8" SCT is running out of gas at about 300+ actual (Jupiter and Mars), but the 10" and 20" are revealing ever smaller features. These smaller features are not well recognized or observed at 250x: The inner structure of the GRS is increasingly resolved, the smallest of the white ovals in the SSTB, red ovals in other belts/near the poles, etc. Very good planetary seeing will show the moons transiting all the way across even when the contrast is somewhat muted vs. the features below. This sort of seeing is not common here, and even on the few nights it does occur, it rarely lasts more than an hour before it degrades a notch or two (diurnal breezes.)
Even on the nights here where I am able to use 350 or even a little over 400x briefly with the 10", things are not quite as stable as I have experienced on the best nights further south. There is another level beyond this, when the seeing is truly excellent, where 500x and above are steady; but that is not for the 10", it is where the 20" will really show what it can do.
Keep in mind that I don't magnify for magnification's sake or based on simple rules of thumb. I stop when I find the optimum for the seeing/scope/my eye: the optimum is the last level that is stable enough to reveal things that might only be suspected at the next increment below, or increasingly blurred/shifting in focus at the next level above.
I am puzzled by calling clouds around Olympus Mons "high contrast." They aren't, or at least not typically. The clouds typically aren't as high albedo as the polar cap, and they are set against some of the brighter terrain. Often they are missing, sometimes allowing Olympus to be detected as patch in its own right, and not responding to filters that would reveal the clouds. They seem quite variable (with the Arsia Mons area being even more so) with level and contrast changing in appearance over hours or days and probably seasonal as well. The visibility is also dependent on the seeing...very much like the white ovals in the SSTB/SSTB which often have only muted contrast with the varying intensity of the beige/tan belts. (As such those ovals serve as indicators of the seeing.)