This is only an opinion, but to me the top pic looks like a Mustang spoiler.
Those are not wide enough because the Charger is definitely a wider car. If I were to want to put a spoiler on my Charger (getting a Daytona, so its a moot point) I would opt to get one designed for the car and not just something tacked on because they have them made for the Mustangs already.
Yep, the SRT guys do use wind tunnels. If it's like the SRT-4, it doens't make "downforce" so much as negate lift. I do note with interest the odd twist and drop right at the ends, right where the airflow from the fenders would be......