I'd be ecstatic if he could turn into a Carl Landry type player. Good comparison, and hopefully he can bring a banger-type mentality eventually.
This may have changed, but it used to be that if you sign a 2nd rounder to a 3-year deal, then you get his bird rights and can sign him to as big a contract as you want. If you don't, you are limited in the amount you can sign him to - at least that's what happened with Joel.
Yes, the rules used to create a situation where a team couldn't match their own restricted free agents if they were a second round draft pick without full bird rights. That changed with the Gilbert Arenas provision in the last agreement. Joel was a different scenario, he was signed as a free agent and not drafted by the team.