I'm fine with them ripping when I buy - provided they are generous as I've had too many fabrics damaged up to 1/2" from the rip - very noticeable in some prints, not so noticeable with solids.
I don't worry about straightening fabric I'm going to cut into pieces. I will straighten backing, and do rip that to get SOG, and then mount on my LA and roll back and forth a few times and that does a great job evening it out before I start quilting.
I use to sew garments, and did a lot of pulling to get fabric lined up. That was always done after prewashing. However often I did not want to waste fabric, so I pulled a thread and cut along that to get SOG.
I prewash all my quilting fabric. Take it out of the dryer and line up the selvage for about a yard, then hold it up with a finger between the edges, and slide one side over until the fold hangs with no ripples. If I've got yardage, I'll work my way down until it's all folded in half, then fold it up from there. The plan was to take it upstairs and ruler fold it, but my folding has not kept up with my purchasing.