There is nothing built-in to turn off only the confirmation emails (you can disable all emails in the settings).
However, if you are handy with PHP snippets, there is a filter hook in my code right before the email is sent to allow other plugins to tap in and determine if the email should be sent or not, and it passes a bunch of variables you can check, including boolean variables for each type of email.
Here’s the code with the filter hook, you just need to return false if you don’t want an email sent, and true if you want it to send:
// Allow other plugins to determine if we should send this email -- return false to not send
$send_email = apply_filters( 'pta_sus_send_email_check', true, $signup, $task, $sheet, $reminder, $clear, $reschedule );