Well if I were to in your shoes, I'd go with a max of 37 inch tires and something like a 4.88 gears. Me personally I'd stay away from 20 inch rims, you have less tire options and they cost more. If your mainly running on the road there really isn't a need for anything bigger than a 35 especially if your only running light trails. My 35 inch tires have done a lot of the trails in Moab a few that I haven't done yet that I might want more tire are Behind the Rocks and Prichet Canyon.
opinions are like a$$holes, everyone has one and some stink