Though I compared him to Suggs for a comp....that doesn't mean I think he is a sure thing. I've got exactly the same concerns that you do about his athleticism.
Some EDGE players, like Suggs, become studs and others, like Gholston, become busts. The differences are subtle, very specific, and difficult to assess.
The only EDGE guys that don't have deficiencies of concern are top 5 picks...they're easy to spot like Garrett is.