1 submission; Courier New; 11pt font.
Printed question and number followed by answer (even put "7. Name:****")
For those who've not had the experience before, this was a lot like a tender writing process - stage one "Expression of Interest". Thousands of people around the world expressing a ton of interest.
Personally, I didn't see much point in doing multiple submissions, after all, D&D has thrived in the worlds with maximum diversity. If you've got two concepts, why not combine them to make one world with more possibilities rather than two worlds with only a few possibilities? Just my two cents.