Been doing some research. Here's what I found out. Please correct me if my assumptions are incorrect.
The configuration in the second picture would be considered a p-trap with a vertical leg, as long as the horizontal trap arm is a minimum 8" long and the pipe size increases one size at the joint. It seems to me that the third option (trap w/ 8" arm then LS 90 to vertical, with increase from 2" to 3" pipe, then a combo wye into the branch drain) would also be a p-trap with a vertical leg.
I also did some reading about "wet venting" which is allowed in the NC plumbing code. I think that the inspector advised me not to dry vent the tub because of its proximity to the lav vent (within 3') , thereby making it available for use as a wet vent, though he didn't explain this at the time.
Any thoughts on this or suggestions for a way to accomplish it?