I went to the Beautiful concert this past Monday. I arrived at 6:15p and the line was very, very long (moved quickly). I was with 4 other people and we ended up getting a decent spot towards the back and on the side. Great view of the stage. No complaints. I don't think both need to be in line together because you set up your blanket/towel on the ground when you get inside and that way you will have reserved the spot for more than just yourself. If the concert reaches capacity before the second person arrives then he/she wouldn't be able to get inside.
I assume The Wiz concert will be handled the same way, but I have no idea if seats will be set up or not. There was a section of seats for Beautiful.
Hope that helps!