Will using both sanded and unsanded grout on your back splash look okay if you have both 1-16 in and 1-2 in gaps to grout?

You should use the grout that will work best for the biggest grout space that you need. So for a grout width like you described, 1/16 to 1/2, you should use sanded grout. Unsanded grout will look terrible in a 1/2" grout joint, but sanded grout will look great in both. Use sanded.