There's no reason whatsoever to disable them, especially Couatl because, since it's a separate .EXE, it won't use any memory from FSX so, it's just pointless to disable it.
The Addon Manager takes about about 1MB of RAM ( which is more or less like a single texture, when you have many hundreds at once loaded in memory ) but doesn't do anything if you are not flying over an area covered by a scenery handled by it so, except with that 1MB of memory, it doesn't affect performances in the slightest way.
So, if your intention is to disable them hoping to reclaim any performances or prevent OOM, you won't get any benefit, and there are other add-on FAR more impacting and invasive you should be worried first.
Of course, as with any other 3rd party module in FSX, then can obviously be disabled with the appropriate <disabled> tag set to True, but this means, if you use GSX, which works *everywhere* you won't be able to use it without exiting from FSX, editing both XML files again, and restarting it. Very annoying and entirely useless, if your goal was to save memory or gain performances, because you won't see any of it.
