The only time you need a trailer converter is if you are using the same LED lamp for STOP/TAIL/TURN. You only need one converter per jeep. (The trailer converters are clearly marked and easy to wire up) If your LED's for STOP and TURN are two separate lamps, you do not need a trailer converter.
The above also applies for incandescent lighting, not just LED's.
Older XJ's used two flashers. One for the turn signals and one for the hazards. On 96 and newer, there is only one flasher that controls both the turn signals and the hazards.