Check with
www.wheelenhancement.com for your chrome lug nut question. Personally, I'd avoid chrome and go with a satin finish that matches your wheels.....and of course, black is always elegant....but I'm biased.
You should not need longer studs just because your wheels are wider. The only reason to use longer studs is if you are using spacers to correct for improper offset. As long as your wheels fill the wheel wells appropriately (no rubbing) without spacers, your studs will be fine.