I wore BDU's a little bit. Yeah, you can get both 1 1/2" and 1 3/4" belts through the loops. I think you will find a 1 1/2" belt will work just fine.
Since surplus has pretty much dried up on woodlands, you are now getting commercial grade, so it's trial and error time. I have found the Propper BDU's are pretty true to spec. I have several pairs in khaki that I use occasionally. The thing is, do you want BDU format or woodland camo (or both). Don't know if you just prefer button pockets, or want the woodland camo.
If you prefer the button closures, then you want the BDU format. But if you just want the woodland camo, then you can probably get ACU format as well, if preferred.
If you go with OCP/Multicam, the surplus is wide open here. You can get these for 20-35 bucks all day long. I would suggest these because of price and availability.
Cammie pants work well, if you are off-road and into to the bush. The extras ruggedness comes into play when you are in close contact with mother earth. But they are hotter and heavier. So if you are mainly in town or out on trails, then the lighter nylon hiking pants work much better. I wear the Wrangler nylon trou (their outdoor adventure line) everyday because they are much lighter then BDU/ACU's. But if I'm patrolling in the woods, I use surplus OCP ACU's.