Re: Breaking in my 2014 GC Limited
You want to vary engine RPMs and loads. Accelerate briskly, then let it decelerate, etc. Hilly terrain is ideal. Long periods at constant speed on flat highway should be avoided. Best to run in sport or tow/haul mode for this because it will hold RPMs better, rather than always upshifting when you decelerate. Occasional full throttle is okay and even recommended in the manual, but not from a dead stop, and do not let it rev to redline.
The specified break-in period is in the manual. It was 350 miles I think on my 2012 - which is not very much. Modern manufacturing tolerances/techniques make all this largely irrelevant anyway, your engine will probably be fine no matter what you do to it.
You also want to let the engine go through hot/cold cycles, i.e let it warm up and then cool down, don't try to "get the break-in out of the way" by covering all 350 miles at one go.