So the auto-draft...basically a computer sets up our draft picks in the order we set our pre-draft rankings and gives us the highest available player on that list, am i right?
Almost! It completely fills your starting lineup, including D/ST and K, before taking any bench players. So if it rolls around to your pick and you already have 2 RBs, but an RB is at the top of your list, it'll go down your list to the next position needed among your starters.
Then for bench slots I believe there's some logic in there to grab you a balanced amount of RBs, WRs, and a backup QB and TE based on your rankings.