Personally, I would avoid the add a leaf. Your factory springs are more than likely worn from normal use. An Add a Leaf set up will give a lift that "from what I have read, I don't have first hand experience" will sag within short time. When I got my Jeep, I wanted something that I could take on forest roads and explore the back country. That aspect did not last long as the Jeep bug bit me and I wanted to see more and go further than stock could do easily.
If you only want to fit a little bigger tire, you can actually put 31 10.5 tires on a stock YJ. You may get a bit of fender rub in rougher stuff, but that can be fixed with trimming the fender flairs. Another option you may want to look at is replacement stock springs. Your factory springs are probably sagged a bit and new springs will give you lift right there without worries of the potential problems that come with lift kits.
Hope this has helped you a bit and welcome to the forum.