I'll give you some guidelines on how to handle this in QuickBooks, Matthee.

The business information in the template is linked to the company name in the Accounts and settings, particularly in the company information. As a result, any changes made to one template will affect the other.

 As a workaround, you can use the Location tracking feature. This allows you to set up each company name as a location with the option to change the details of one without affecting the other. Please note that this is only available for the QB Plus version. 

I'll show you how to do it:

1. Go to Settings and select Account and settings.
   
2. Choose the Advanced tab.
3. In the Categories section, click the Edit ✎ icon.
   
4. Toggle the checkbox to track locations.
5. Click Save, then Done.
   

After which, you can add a location by following these steps:

1. Go back to Settings, then select All lists.
   
2. Pick  Locations.
   
3. Select New, then add the Name you want to track.
   
4. Click Save.

The next time you record an invoice, you don't need to create a template but ensure to select the correct location.

I've included some resources you can read on personalising your sales form for future use:

• Customise sales forms by location.
• Customise invoices, quotes, and sales receipts in QBO.

Feel free to visit again if you have other questions. I'll be around to help.