an strap him down and put him in a cage. Were there any other characters in this same position? what happened to them?

Your quote refers to Slim talking about what would happen to Lennie if he was caught and not killed. I don't think there is another character that is really like Lennie. The men think Lennie took advantage of Curley's wife and killed her. Lennie's mental incapacities would not be considered very much. If Lennie managed to survive, he would be placed in a cage. The men on the ranch were afraid of Culey's wife. They fear Curley will fire them if they pay attention to her.