Hi Achilleas,
1) If you want to disable sending review email to the client, you have to disable this from a plugin. Please find a system plugin named something like System - Taxibooking Schedules Plugin from Backend Plugin Manager and click to enter on edit page. You will see an option Enable Archive Orders, you have to set this NO to disable sending automatic review email to the client.
2) Currently to edit the email content, you have to edit email template files in the directory here SITE_ROOT\components\com_tbsaas\templates\order_emails. confirmation_email.tpl.php is for the new order notification email and archive_email.tpl.php is for the review email of an archived order. But, please be careful while editing those files as order information are replaced by PHP variables there. If you need these email templates easily editable using backend email template wizard, please submit a new development request here. Also, please remember that all your customization will be overridden on next LIVE update and we do not provide any support on any customized feature.
Hope this helps
Thanks a lot
Ronniee