It seems we have a similar problem. At least, it is nice to know I am not alone.
1) I am thinking the only reason we got our NOA2 so fast was due to no additional RFE.
2) The NVC contact people were frustratingly vague about their role in the process and timeline. Did you receive ANY communication from them, confirming receipt of your case? We did not. We only got our case number after I called them directly to confirm they have created our case in their system. I was under the impression from the research we did, that we were supposed to receive a letter with our case details and invoice number in the mail.
3) Agreed the DS-160 thing is frustratingly vague. The NVC's own process guidelines don't seem to match up with the actual processes they follow when questioned about it (Eg. the welcome letter package not being sent out)
4) Thank you for commenting, and I will do the same if I hear anything on our end.