Structure Detection - trying to learn

I'm trying to better understand the "Structure Detection" preferences in Calibre conversions.

1. Is the purpose of "Structure Detection" primarily (or entirely) to determine where page breaks are inserted and/or files are split? Anything else it does?

2. Most of my ebook conversions are EPUB to AZW3 or MOBI. If the EPUB is well-made, with each chapter and section split into a separate file, can I safely set Detect chapters to "/", Chapter mark "none" and Insert page breaks before to "/"? Will doing this ensure that the resulting AZW3/MOBI has the same page breaks as the original EPUB?

3. Occasionally I build my own ebook from a single HTML file using <h1> and <h2> for chapter headings. If I specify <h1> and <h2> for chapters in the Table of Contents prefs and use CSS to insert the proper page breaks (page-break-before: always), can I leave the Structure Detection settings "off" per above?

4. If I leave Structure Detections settings "off" per above, will that have any affect on how the Table of Contents is built?

Thank you for any insights and enlightenment!