#1
How small are you wanting to go? I personally like the look of 18'' Titan Fast Trekkers on a 110. They are low profile and it will be a rough ride. Or, 18'' Turf Tamers will give good traction and and look cool as hell too.
#2
As far as K&N and UNI goes, it all depends on which one like better. There really isn't a difference in performance. If properly mantained, they both filter the same. I would save a few bucks and get the UNI.
"I am going out of this world.....the same way I came in...screaming and covered in blood."