Either way, at the same time or having the docs + fee sent first and then request NOL.
Your home country embassy is responsible for sending the NOL directly to DoS, so it will also depend on the Embassy's processing time to prepare and mail the NOL. They might ask you a few letters and documents (mine did) in order to prepare NOL.
I've read here that some people suggested to have NOL sent only after you can see the documents and fee updated on the online database, but that's not a official recommendation of DoS (at least I didn't see it on the instructions), and for most people doing both at the same time seemed to have worked well.
--I am not a lawyer so act accordingly--