Yes, that’s correct. The “scoring output log” and “scoring error log” only show up if the evaluation script writes something to standard output or standard error, which would typically only happen if there was something wrong with your submission. The scores that your submission got are indeed in the “evaluation output from scoring step” download, specifically, in the “scores.txt” file.
There’s no way for a participant to delete a submission, but you do get to select which of your submissions gets posted to the leaderboard; there should be a “Submit to Leaderboard” button alongside each submission on the “Participate” page. The “Trial” phase is set to allow you up to 100 submissions though, so hopefully that should be plenty of submissions to test out your setup. If you still really need to delete a submission, let me know; as an administrator, I can do that.