Tires Sizes? So Many?!

[96FMF300EX]

ive been reading all the tires posts and im trying to make a decision on the size i am going to purchase. I have decided to get the Maxxiz Razr's all around from rmatv with the .190 combo. Im set on the 20/11/9 Rears. What will that do for the gear ratio or top end? or will it affect it at all? and i have a 14t front sprocket. and im not quite sure on the front tires. they are the same price so it doesnt matter but either the 21/7/20 or the 22/7/10. which would be better? most of my mods are at the bottom so if you need those there they are and i most trail ride and knock around the farm. let me know what ya guys think and oh ive never bought tires before do the combos come with 2 tires and rims and the tires already mounted?

thanks
96FMF300EX