are rec letters helpful for panhellenic recruitmen

I'm rushing in the fall and I have family friends that are sorority alumni that are willing to write rec letters for me. I've heard that they're helpful, but if I get rec letters for say, five sororities, does that mean the other three probably won't want me back because I have rec letters for other sororities?

Also, how often do people end up rushing their legacy? I went to greek preview and honestly the girls I met from my legacy house I didn't click with at all and they seemed kind of rude.