I have added custom form styles for our Estimates, on preview they show just fine but the document we send to the customers does not have the design options

Let me explain inputs when managing custom sales form templates to send them to your customers, Obakeng.

If you're referring to the design options when creating an Estimate entry and sending it to your clients, you can only modify the form template under the Manage tab. Then, make sure to choose the correct and saved form style. I've included a screenshot for reference.

In addition, QuickBooks Online depends on the setup preferences created for estimates, and unusual behaviors like this may have your templates being corrupted.

With that, if you've selected the right form style and still the estimates being sent are incorrect, I suggest recreating the customised quote template. Add them to the transaction and send it to your email to verify and help rectify issues on your sales form entries. For comprehensive steps, refer to this guide: Customise invoices, estimates, and sales receipts in QuickBooks Online.

Moreover, I've added this reference to help you track and record customer-paid invoices in your file: Record invoice payments in QuickBooks Online.

Please let me know anytime you require additional assistance when managing sales transactions in your account. I'll be around in this thread. Stay safe, and have a good one.