What size tire?

[Muddy13]

Hey guys I am new to the truck game but have done lots to jeeps in the past. I recently picked up a loaded 2013 1500 bighorn 5.7 I was planning on doing bilsteins set to about 2.5 and Moto metal 970 wheels and number 1 was debating whether to stick with 20 inch wheels or go down in size and also what size tire can I go without rubbing issues or other issues in an m/t or aggressive at tire. Thanks in advance