If a user has 2 or more quicklook plugins that handle the same kMDItemContentType what happens? Which plugin gets priority to do that actual work? Can that be set programmatically?
From a quick reading of the docs (Installing Quick Look Generators), the Quick Look daemon chooses a generator based on the following search order:
MyApp.app/Content/Library/QuickLook
~/Library/QuickLook
/Library/QuickLook
/System/Library/QuickLook
They finish by saying that if there is more than one generator for a UTI, the one that ranks highest on that list is chosen. If there are two or more for the same UTI at the same level, Apple says there is no way to know which will be chosen; the generator that is found first in their search is used.