Tim Williams is probably not a possibility for Miami because of system considerations.
Cunningham looks to me like a nice cross between Karlos Dansby and K.J. Wright. He's very tall and lengthy but plays with great knee bend so he seems to never have leverage problems. Takes on blockers really well, very physical. And he's got good range, can run all over the place. Physically in terms of build and ability he profiles like a guy the NFL will love because he can be very good in coverage which has become more and more important in today's NFL. Interestingly though, his run defense seems to be ahead of his coverage, and he's a compelling run defender. That's where I think the Wright and Dansby comparisons hold, because those guys were destined to have a brighter future in coverage at the NFL level than they did at the college level. Not that any of the three are/were bad in coverage at all. I think you're just looking at linebackers that are total play makers and good run defenders who had/have the ability to end up elite in linebacker coverage as well.
For the kind of defense Miami wants to run, Zach Cunningham seems the most obvious fit while being an excellent, excellent player.
That said, Anthony "The Franchise" Walker, Jr. may be the best linebacker period that they could be adding and there is something to be said about that because every year it seems like coaches may want to run their system a certain way and then the plans have to change because the players are good at some things and not good at others. Miami's defense wants to pattern after Seattle in many ways, I think, and one thing to consider there is that Miami may already have a K.J. Wright-like player in Kiko Alonso, and perhaps they ought to get themselves more of a Bobby Wagner in Anthony Walker.
Either way, I adore Walker. When the draft process rolls around and starts going in earnest, you're going to start hearing a lot of stories about Walker. Very Myles Jack-like. He's from Miami, and I would love to bring him home.