The stock 16" wheels are blacked out aluminum (under the hub caps) that some choose to run that way because they like how they look. I doubt you could ever achieve a weight difference that could have a performance effect you could actually notice. You don't take your Niro to the track do you? What you will notice from wheel/tire combination changes will be handling, noise, and comfort. There are a lot of combinations! But you can start by test driving a Niro equipped with the stock 16s and see how you like them.