If your primary concern is your warranty stay 110% stock.
I asked my dealership on day one what they didn't want me to do to the car, and they said I had free reign. It's also my 3rd car from them. Each time they have made money on my turn-ins.
Going by the US flag on your avatar...This horse is glue by now. Mods do not void warranty in the US. If a part can be reasonably proven to contribute to or cause something to fail, then Kia has the ability to deny warranty coverage for that specific failure.