You did a beautiful job with your fabrics and piecing. Will be looking forward to seeing it when it's all done. Keep up the good work!
As for prewashing VS not, try it both ways yourself. That's the best way to decide what works for you. There's pros and cons to both sides.
For what it's worth, I'm a pre-washer, not only for getting off the sizing (starching is the backup when needed) and color bleeds that aren't anticipated, but it's been my experience too, with quilt shop quality fabrics as much as other shop fabrics, the hot wash and mild dry pre shrinks the material, which helps me and my confidence level that it won't do anything "weird" once a project is done and ready to wash for the first time. Those are the reasons I have chosen to prewash. It may not work for everybody.