Cool top! If it is going to be a wall hanging then invisible thread is fine. I don’t like using invisible thread on a bed quikt but that is just my preference. I think if I was going to do line quilting, I would space the lines closer together like in modern quilts. If you are quilting on your sewing machine, I might do the lines across the quilt since those lines will be shorter. If you have a long arm, I might mount it sideways and use the channel locks to do narrow lines vertical.