After much debating, I ordered 285/70R17 duratracs for my '14 JKU with no lift for now. I've been told by the shop that there shouldn't be any issues with these tires on 4.75 backspacing wheels. I've heard only good things about the duratracs so I'm excited to try them out.
I suspect depending on which type of lift you get, you may or may not affect the warranty but only for the suspension portion. Obviously if you change the shocks and springs, you will no longer be covered by factory warranty for suspension. I'm not sure though how a spacer kit or leveling kit with factory shocks/springs will change the warranty. I can imagine some dealers will give you trouble for altering the factory suspension. At that point though, you should probably take it up with whoever's doing the lift in the first place. Just my 2 cents.