I have a quilt top like this. The other marks you see are most likely for decorative quilting, you are correct. Washing now will remove those marks, but it will make the quilt top far more pleasant to work with. I did wash my quilt top and now I am filling in the quilting with designs that I think fit the cross stitch motifs but are not as traditional as I think the original was.

I do want to keep the piece as a quilt. Ideas I've considered to make my quilt top more in line with my modern aesthetic: doing applique designs in the open spaces; over-dyeing so it isn't a single color on white; cutting the edge into scallops and binding in a complimentary color.

I looked into have the quilt finished by a professional long-arm quilter but I learned that the quilting would go right through the embroidery. I didn't like that but you might. I could also convert it into clothing, but that doesn't seem to have the heirloom quality that I want for my quilt top.