The easy answer is support it within 3' on either side of the conduit body (<100 cu/in) and it doesn't matter.
The exception allows you to virtually ignore the conduit body if it is the same as the raceway size and the raceway is supported properly. It is just a bump in the pipe that requires no special support.
As soon as you start hanging devices you are moving down to (F) and you need support at 18" from both sides or 12" if it is one pipe (d).
