Vaughn, Arnoux and Morstead are all special-team standout type players in year 1. Vaughn is a vicious hitter, solid tackler, and a guy who has been known for blocking kicks. Arnoux was rated the 2nd fastest linebacker in the draft (after teammate at Wake Forest Aaron Curry) and he is also known as a terrific tackler. Morstead, according to Sean Payton, is the guy they labelled as having the strongest leg in college football. So don't expect Vaughn to unseat Roman Harper, and don't expect Arnoux to cost Scott Shanle a roster spot. What you can expect is that the Saints special teams will be much better with these three guys than it was before the draft started. Glenn Pakulak seemed like a punter who filled in nicely last year, but he'll have his work cut out for him this offseason with one heck of a training camp battle against Morstead. Even if Morstead ends up released in favor of Pakulak, you have to assume the Saints will be better off at the position for it.
Malcolm Jenkins is a whole other story. We'll have to see how things develop over training camp and preseason. Right now the Saints are looking at Darren Sharper starting at FS and Jabari Greer/Tracy Porter at corner. They love Randall Gay as their nickel guy covering the slot, so he's probably not moving from that #3 corner spot. So now it remains to be seen if Jenkins can unseat new free agent Greer or 2nd year man Porter. I think that's unlikely based on his "tweener" status coming into the NFL and questions about how successful he can be at the cornerback position. I think Jenkins starts #4 at CB with a move to free safety very likely. I see him starting year 2 at free safety, succeeding Sharper, depending on how things play out at cornerback. The Saints had so many injuries at that position a year ago, he could easily be in the lineup by midseason if not sooner. The good news is Gregg Williams' defense has a lot of different wrinkles that plays into an individual player's strength and it relies heavily on rotating personnel. This means there will be room on the field for Jenkins provided he is healthy and lives up to the hype.