I doubt the left over day madness will be any different due to the new secondary draw. CO always had the secondary draw, but it used to be limited to unsuccessful primary draw applicants (and called the leftover draw) where this year it was open to everyone. The only tags on the list were ones that nobody wanted/drew though, not returned tags. All the returned tags will still be available only on the leftover list (unless it was over 4 pp unit then it goes to the next in line people).
Also, all the returned tags will be available on leftover day (4 Aug) as long as they were returned before 3 Aug). If returned after 3 Aug, that's when they get put randomly on the leftover list.
All this is spelled out pretty good in the regs linked above though.