So when registering for a particular (USCF sanctioned) event, there is an option to register under OPEN or several subdivisions of reserve (based on ratings range, to eventually an unrated section)

The reserve section's games start at a different time than the open, and I was wondering what is the difference between registering under one rather the other if say you are unrated. for example, do you only play against other unrated players in reserve, all of reserve, or reserve and open players? (there are about 80 players total)

This is important because I initially registered under "reserve unrated" and after looking at the spreadsheet of participants, there are only 2 other unrated players, and I don't want to play a tournament against only these two, and if this is the case, I would rather register in the open despite playing against more talented players

In most open tournaments, the unrateds play in the reserve section, meaning you'll be playing against rated players, though the ratings for the reserve are normally under 2000.  You shouldn't have to play the other unrated unless two of you win or lose all your games--then the pairings will forced.  But, if there are only two others, your chances are that you would only play one of them.  Good luck, and I hope this answered your question.  If you have any other questions, feel free to contact me.

Ok thanks, so the subdivisions of the reserve is just for seeding, I understand now :)