I suggest you read 'Study Size' under 'Methods'. Detecting an odds ratio of 1.3 with 80% power, and rounding way up to 3000 cases. To me that's not a small sample size, but definitely not the highest OR to aim for. Different cases vs. controls is not a problem for this study design. You pointing that out as a negative makes me think you might not know as much about epi study designs as your comment lets on
