Just came on to post that. He has all the athletic traits of Hill and they let him go there for a 3rd and change. Presumably they think he'll be a bust, those fast guys are often over drafted, but Reid selected Jackson and Hill so he knows what he's doing when it comes to that type of player.
In terms of Penix they are paying him reasonable back up QB money so if it was just a short term concern over Cousins there are more cost effective routes to take. They must have a bigger plan, whether that's injury related or think they'll be able to trade Penix relatively soon. He's also not a younger prospect and QBs drafted that high don't normally sit for all their first season, so they've created a QB controversy straight away.