Use the in-game profiler, you need to save profiles for axis, and buttons, so two for each controller, the throttle is a totally seperate controller from the stick, their both seperate from the keyboard, so to save your stick profile, click on an axis or button in the x-55 stick category, then save it, then to save your throttle profile, click on a button or axis in the throttle category and save it.
yes, you need to set controls for every plane, all the fc-3 planes really could just be 1 profile, since their all simplified down to the point where they basically use the same number of keys for the same systems, even if iconography, locations and names are slightly different visually in the cockpit... but their not 1 profile...
but for the non-fc3 planes, there are enough differences between them that, although there are still a lot of controls you can set the same for every plane, you do need seperate profiles for them.
unplugging your stick and throttle won't affect profiles, just make sure to plug them in before you start dcs.