If your wondering if it will do anything the XJ would Id say it will do 80% of what it would do. The Wrangler and the XJ are in their own league. Then comes the rest, the KK will do anything any other 4x4 can do pretty much with better suspension and tires. Once you put the new suspension on there, the ride will be much better for sure. There is not as many options to build up the KK, you only have a couple suspension options, couple this and that options. But you can build one up pretty well if you want and be one of the few rarer Jeeps on the trails.
Seeing as you went thru all this on the XJ, get the arms while your doing the lift and be done with it. Some with say they did not need them, others say they were hitting on the big stuff without em....With what little options you have, add the arms for the extra clearance they give and when your lifted they look nice as well ,and we all know looking cool is part of it...For lift, Id say the OME is the most popular with TM Eco lift being a close second. You cant go wrong with either for sure. I did the OME with top plates and extra ISOs in the back for a full 3" with Bilsteins and Als A arms, very happy with my choice. It was stiff for about a month or so, then it smoothed right out and its good to go now.
Again with you beefing up your old XJ, keep ATtheHelm in mind, hes a member here that does all sorts of stuff for KKs, from roof racks\rails to big bad azz bumpers front and back.