I too did some research on Rapp this week. I mostly read the opinions that Rams fans posted when the team didn’t keep him.
The overall vibe was that Rams fans were happy he was gone. They said he is slow and coverage is not his front suit. Said he should be more of a LB, which is actually how the Bills have used him thus far (Big Nickel). Some said he was frustrating because he could have a great quarter, followed by a terrible quarter. They felt he was too inconsistent.
However, we have something that his previous team didn’t. McDermott. Who tends to turn DB’s into very good players. Look at the drop-off Wallace has had since leaving. Anywho, if anyone can harness Rapp’s tools, it’s McDermott.