I quilt on a long arm and my stitches aren't always the best due to me moving too quick, especially around curves, which is what I love to quilt, and that is why I use the same color in the top and bottom. If your machine makes a pretty stitch while free motion quilting, then you won't have that problem. King Tut has some pretty variegations. I haven't sewn or quilted with them although I do have several spools. Maybe someone else has used the specific type thread you are talking about and will know the effects of the different threads on each other.
I would try to match the weights of thread, but that's just me. I mostly use a 40 weight trilobal when I quilt.