This measurement is called “projection” and can be found in the images on our product pages at our retailer partner websites. Generally, square shaped pulls will have wider projections for larger hands or knuckles. Here's an example for the solid bar pull.
Yes. Delta® or Franklin Brass® shower grab bars can be installed on fiberglass walls, but only if they’re anchored securely into wall studs. This ensures the grab bar can support weight safely. Always check for stud placement before installation.