I use the ply that is best for my truck. I don't haul anything and ply does not give sidewall security against things on the trail in my experience. You can tear all of them. It WILL give you worst gas mileage especially if you go up a tire size or three like I have on my Tacoma. Then you have to regear the vehicle, and the shift points are all weird etc.
I use the Falcon Wildpeaks, great in the snow and good tread in the dirt for an all terrain. The Toyos open country are a good tire too.
Like I said, I went up a few sizes to get another inch in diff clearance, plus I have fox shocks with a 1 inch lift. Like someone else said, air down to about 15 psi and you will be good if you have the clearance. Max trax is a good thing to invest in as well just in case. Lockers are good to have too. I would have put one up front but I'm pretty sure it doesn't work well with IFS, so rear factory locker it is.
For water, say a flood in monsoon season, or just a water crossing, I've never been so deep that I was worried. I think next year I'm going to do diff breathers, but I don't think I'll ever need a snorkel. My diffs have been under water in mud through.