It really does not make a difference which rack you use. IMHO the placement of the meat has to do with if you need to get access to. If this is a bullet style smoker use the higher rack, just easer to get to and manage.
I do 4# butts all the time IT of 150 after about 2.5 hours is about right, It will stall so it will slow down. I agree wrap it at 160 then let it go to 200 then it can rest.
I think you are on the right track the only concern I would have is the smaller butts will rest just fine but if u have...
Here are the rest of the pics,
Right before cutting rested for 15 minutes.
Sliced and ready to go
On my plate, ready for my belly
This was a real winner, we were all surprised by the smoke flavor the tenderloin had, one of the smokiest flavors we have had to date. Moist and tender...