Often people piece with 50-60 wt thread, quilt with 40. It is ok to use thicker thread for quilting if you want your thread to stand out. Piecing most want finer thread so their piecing is more accurate. Heavy thread takes up space in the seams so when you think you are sewing a 1/4” seam it may take up 3/8” or more when pressed. I know quilters who quilt with quite heavy threads sometimes when they really want the threads to show- be a dominant part of the quilt- even 12 wt.