What is the difference between a walk-on tryout and a recruited walk-on?

A recruited walk-on is when a student-athlete is recruited to the college by the coach and offered a spot in the program ahead of the school year starting. Some coaches will treat this like any other roster spot and verbally guarantee that this player will remain in the program for the full year, other coaches will treat this more as a tryout position and will not guarantee keeping this student-athlete on the roster for the entirety of the year. This is an agreement that is made between the coach and the student-athlete. There is nothing that legally binds the coach to honor this agreement. 

A walk-on tryout is when some colleges will hold an open tryout at the beginning of the school year in order to see if any of the general students that have enrolled in the school are skilled enough to be on the team. There are no guarantees that anyone will be offered a spot from the walk-on tryout, and if someone is offered a spot, there is no guarantee how long the coach will keep that player on the team. That is an agreement that is made between the coach and the player. However, there is nothing that legally binds the coach to this agreement. 

As a recruited walk-on, is there anything I would sign?

There is no binding agreement that a recruited walk-on will sign. NLIs are prohibited for anyone that is not on any athletic scholarships. Most programs will have their recruited walk-ons sign documents that are called Intent to Enroll forms, which are standard forms that colleges will have general students fill out to inform them of their decision to enroll in their school. This is really not a binding agreement, and there are no eligibility implications should the Intent to Enroll be broken. Often times; a student can fill out an intent to enroll with one school, and then decide later on that they do not want to attend this school, and can opt to decline enrollment and sign an intent to enroll elsewhere. There is no legal implication on either side if a student-athlete or a college coach does not honor a recruited walk-on offer.