PayPal Express is not one of the 3 main options but a suboption of 2 of the paid PayPal options.
I can only select PayPal Express IF I select one of the first 2 PayPal options : Pro or PayFlow (which is ONLY a gateway). But if I select either, I need to enter in all the information of a PayPal account which I don't have access to. I just have the account business email address which is all I need to send the payment.
Here are 2 screen shots.