There are controlled scrappy and just scrappy. Your quilt can be done however you want it. I have grown to really like just scrappy and think they look really good. My Daughter does mostly just scrappy and that is what she likes, always looks good to us.
I would not use the thinner stuff with the better quality. I would use all the thinner fabrics to make a dog or cat quilt or a utility quilt. I would not mix them in the same quilt. Just my opinion.