When you use your extensions control panel, it's far better to change the view to "As packets" As 9 times out of 10, it will make it obvious what extensions are used by which app. Also, Click on the little "Show information" triangle thingy near the bottom left of the control panel window. Now when you click on an extension to highlight it, it will usually give you some more useful information about it.
Doing both these things should help you a lot in deciding which extensions you can and can't disable. But if niether of those idea's help, then it's just a case of trial and error..