Hello,
Please, find below the answers to your questions.
What is the payment url for express checkout?
The payment URL that is specified in your PayPal Express checkout Payment system should be always 'payments/paypal_checkout.php'. Please, do not change it in any way.
What is the cancel url?
The cancel URL is {site_url}order_final.php
What does passed / not passed mean?
It means what parameters will be passed to the Payment URL script. In case of the PayPal Express Checkout all parameters is for an internal use only so all checkboxes 'Not Passed' are checked off.
If those options are checked, does it mean they are passed or does it mean they are not passed.
For this particular payment system it means that all these parameters will not be passed over GET or POST method to the script paypal_checkout.php, however a script gets all these data directly from the payment settings rather than from GET or POST method and all these parameters will be used to generating requests to the PayPal system.
Which options should be passed?
Please, do not make any changes to the default settings and all boxes should be checked off as 'Not Passed'.
Do I need to set any advanced parameters.
You do not require to set any advanced parameters for Express Checkout. Such parameters are required only for a PayPal Direct method or for other payment systems when a customer submits credit card details on your site via SSL connection.
With regards,
ViArt Support Team