The gist seems to be ...
Seriously, folks, the
only answer is to do what your editor says, and follow your publisher's instructions and/or style guide as supplied.
If you follow advice from here or otherwise obtained from other authors the odds are about 1000:1 that you will
not be doing what your editor and publisher want, and you will be making more work for yourself and more work for them.
I'm really serious here, editors get very frustrated indeed with authors who not only don't read the instructions and don't do what they're told but also waste vast amounts of time and effort following advice from third parties doing things which are at best a waste of time and at worst seriously conterproductive.
What works for one publisher's production process could seriously bugger up another's - ask
your editor what is needed and
do what you're told. Apart from speeding up the production of this book, this will greatly enhance your chances of ever getting a contract for another one.