They can be plugged in with the included pigtails.
The PWM on the Jeeps does create power fluctuations in headlamp voltage, not noticed with regular lights, but noticeable with LEDs. Rallylights and other sell additional harnesses for under $150 that eliminate that issue entirely.
I have been running the 7 LED headlamps in the picture for almost a year without a harness and hardly notice the flicker. However, I am also adding the harness with the newer lights when they come in.
I assume btw that you are talking about the headlights only, but all the other LEDs are straight plug and play, other than an occasional wire splice and/or a relay. Even my taillaight are LED, and the headlights are the only ones where the stock wiring is inadequate.
- Bill (formerly VetteDriver)