Alerts: In the appointment, scroll down below the time. (It doesn't appear as though you can scroll, but you can.) You'll see "Alert" with pulldown options.
I don't think you can make "email" the default on the Mac. Your calendar/email provider may perhaps provide this option.
If you already have an event set up with an email reminder in Calendar you can option-drag it somewhere to make a copy of the event and then edit the other details as usual.