I've manually edited the _login.cshtml file to comment out New and Login features.
The Guest account radio button is on by default 'true'

The EMAIL text box is only one showing, commented out Username and two Password boxes.

Every time entering a correctly formatted email address on checkout, it throws a format error and must be re entered.
Email validation works second time around as long as it is correct format.

Is there a way in the back end to disable creating account and default to guest checkout?

Is there a way to troubleshoot the validation for email?

Thanks