You should get an SYE regardless for 3.5 or 4.5I believe youll need to SYE with the 4.5"
I have the RE 3.5 superflex kit and its fine for 33's and 35's would fit fine with bumpstop adjustment. From personal experience, I think the 3.5 lift gives more stability over a 4.5 lift on an identically outfitted rig. My bother and I have TJs, both with the set up exactly the same but one with the 3.5 and the other with the 4.5. Mine is noticeably more stable in off camber spots.
I ended up putting a 1.25 Body lift and 1 inch motor mount lift so that I wouldn't have to mess with bump stops.