Watkins-I believe he fills that 4T LE role in our base defense. This spot in Quinn's scheme is more like a 3-4 DE that anchors and holds up multiple blockers. He certainly can play a little 1T in a pinch as well.
Urban-another 3-4 Defensive Lineman who has starting experience. Think he fills that Tyrone Crawford Role. Can play inside/outside, known more as a high motor run defender.
Basham-might be the Aldon Smith replacement and an upgrade over Armstrong as the #3 DE. Many think he was not used correctly as a stand up Edge rusher, where he is better suited as a down pass rusher. More of an upside pick.
These are more role player, rotational types that improve our depth. Behind the starters, we either have young prospects or undrafted fa's. These moves were necessary and could make a difference in the long run.