Services that are for registered users only will invite users to login/register from such URLs. Leave blank for WordPress default login and registration pages.
Reservation status page
When visited from the reservation status link inside a confirmation email notification, the frontend widget will show all the customer's current reservations and their statuses.
In order to make the link work, you have to select here the page in which the plugin shortcode is. It can be the same page in which you are accepting the reservations, or you can create a new one, just for the reservation statuses.