Thanks for posting again here. Let me assist you with the invoices.
Yes, the total amount, as well as the taxes, will show on the invoice since it is the default regardless if you used a customised invoice template. Before sending the invoice, click the Print or Preview button at the bottom to see how your invoice looks like
If there are no taxes showing, the most possible reason for that is that you haven't set up your VAT yet. You can follow these steps on how to set up the VAT:
Go to the VAT menu, then select Set up VAT.
Select your Start of VAT period and your tax Filing frequency.
Choose your Reporting Method and enter your VAT Registration No.
Tap Next, then select OK.
I've added some articles you can check. These will help you to manage your taxes in QuickBooks Online: