I just completed one bib. I must say it is very cute. The seam width is dependent on the piping. I used the piping that the pattern calls for and the seam width was approximately 1/4". I also made the first one with the batting and it is a little heavy. I like the idea of using a flannel material for the back of the bib. Next time, I would buy 3/8 of a yard of the main fabric for a one way print.
I just found this pattern and it will be just perfect for baby shower presents. I think that the seam width will be determined by the width of the pipping you use.
I haven't made this project, but it would have been good if the seam widths were included. I will probably use a 1/2 inch seam. Also, an option of not including the pocket and instead embroidering might be nice to include. Finally, rather than use nursery fabric and batting, jut use a backing of cotton flannel or terry as an alternative.