I will start of by saying that I know very little about Enlightened Equipenet quilts, so Tim's advice about his own product is of course the most experienced.
I would just offer an option based on a different system:
You say:
Cold sleeper, slim build, calm sleeper.
10F Possible, 20-30F common, 50F possible, you want a lighweight option to do it all.
My option:
10F Regular fill, regular width quilt + breathable bivy. This saves 4oz in the quilt over the overfilled WIDE Tim suggested, and adds about 6 oz back for the bivy, but might save you weight in a groundsheet.
Since you are slim and calm sleeper, I am guessing the regular width to be plenty wide, I have the wide and it is huge! The only time you might need that extra width would be for draft control in the coldest nights, but the bivy takes care of that.
The lack of overfill would make it less warm, but even as a cold sleeper, a 10F rated bag should be good in the mid 20's for a cold sleeper, which you mention are the most common conditions in fall. On the rare 10F nights, the bivy and some good warm down clothing will take care of your 'colder than average' metabolism.
On the other hand, the slightly thinner bag will be lighter and less sweaty on the 30's and 40's nights, and if it turns out to be 50's you can always sleep in just the bivy, instead of being completely uncovered. The lower fill will also allow you to shake the down to one end for us one warmer nights.



