I've learned
To stick to one machine/one foot for the entire quilt.
A 1/4" foot and a quilting foot for a 1/4" seam are not the same. At least for the feet I have purchased, a foot labeled 1/4" is a true 1/4", and a quilting foot for a 1/4" sem is a scant 1/4"
If I really need to be exact I do try to oversize the block units, and then trim them down.