Thanks for following up with the Community, RC125. I appreciate your detailed information.
 

I can certainly understand how an ability to switch back to the old invoicing and estimates experience could be useful and have submitted a suggestion about it as of today.
 

You can also submit your own feature requests while signed in.
 

Here's how:

1. Use the Gear icon, then go to Feedback.
2. Enter your suggestion(s) in the Have feedback? window.
3. If necessary, attach a file with your Camera icon.
4. Select Next.
   
   

Your feedback's definitely valuable to Intuit. It will be reviewed by our Product Development team and considered in future updates. You can stay up-to-date with the latest news about your product by reviewing Intuit's Product Updates webpage.
 

You'll want to be aware there's a few classic invoicing features that aren't available in the new experience:
 

• Mobile classic sales tax
• Billable Mileage Tracking
• Add previous attachments
• Mobile multicurrency
• Reference links displaying matched online transactions
• Price Rules (they can be created, but not used on invoices currently)
• Mobile subtotals (they're available in your web version)

You can learn more about the new invoices and estimates layout in our See what’s new with estimates & invoices article.
 

In regard to sales taxes showing on sales forms when they're turned off in QuickBooks, our sales tax article mentions that if you had sales taxes turned on, but don't charge them, you'll need to turn them off before using your new experience.
 

Since yours were already turned off like you say, but are now showing on sales forms, I'd recommend getting in touch with our Customer Care team and bringing this to their attention They'll be able to pull up the account in a secure environment, conduct further research with you, and create an investigation ticket if necessary.
 

If there's any questions, I'm just a post away. Have a lovely Thursday!