When I do PPing, I use a 1.0 stitch ... and sometimes I even shorten it further.
The papers come off easily, with no disruption to the stitches.
The general rule is no backstitching when PPing or anytime in quilt piecing, as you are later going to stitch overtop of that seam, when you join in other pieces. When it is an outer seam (eg. on a border) where no overlaying will be done, then yes, a lock stitch or a backstitching is done to prevent stitches coming out.