Very helpful, thank you.  In summary,

• leave Create Days in Advance blank.  
• Choose Automatically send emails.
• Set Repeat to Monthly
• Set on Day to the day of the month you want the invoice sent out.
• Set the Terms in the invoice window to be the number of days after the invoice is sent out that the invoice will be due.  So, for instance, if you choose the On Day to be the 9th, and you choose Terms Net 10, then the invoice will be due on the 19th every month.
• Set the start date to be a few days before you want the first invoice to be sent.  So for instance, if today is August 6, 2024, and you want the first invoice to be sent out on September 9, 2024, you could set the Start date to September 1, 2024.

There does not appear to be a way to actually preview the invoice that will be sent.