Responsive Shop Member Accounts Not Disabled

I’m running Responsive Shop Theme 8.9 with Style 2 Child Theme 1.0, and want all membership account settings and features turned off – using Guest Checkout only – with these options settings:
-Responsive Design: On
-Guest Checkout: On
-Enable Users Registrations: Off
-User Passwords: Off
-Security Code: I’ve tried both On and Off; currently Off
-Enable User Profiles: Off
-no member or account login entries in any menus
-no caching nor membership plugins in use
-Checkout Step 1: Checkout Options language changed to text shown in attached image.

Customers are still somehow successfully registering accounts and being emailed the standard “Your username and password info” emails containing their registered username and system-generated passwords. These accounts now show up in the WP Users tab.

The only way this is happening that I can figure out is that the disguised Checkout Options buttons are being clicked, rather than the Guest Checkout button, taking customers to the account creation code. So I’d need completely custom Checkout code to eliminate those buttons, wherever that would need to go.

Anyone have any ideas on where to look or what additional settings are needed to fully turn off member accounts and stop these username/password emails from being sent out? Any suggestions appreciated. Thanks.