Hi there, @tgweydert.
It could be that the Save and send option was selected when the invoice was updated. This is the reason why your customers are getting another email every time you made changes to the transaction.
I'd recommend clicking Save or Save and close when updating an invoice. This way, it will only be saved inside QuickBooks and you're customers won't be notified.
Additionally, there are several financial reports you can run to track your sales income in QuickBooks. They will show you helpful insights on the things you buy and sell, and the status of your inventory.
Let me know how else I can help you with QuickBooks by adding a comment below. I'm more than happy to lend a helping hand. Keep safe!