When are Rating Review Emails sent out?

An order needs to be in a 'Shipped' status before the review/rating request is sent. 

How can I view the rating / review email content?

You can view the order, then click on Print/Email docs, then choose the VIEW button next to Review/Rating request, so you can see what it would look like. 

Can I test the what they email looks like sent out via email?

You can run a test order on a live website waiting the set duration once shipped, but not on a trial website. On a trial website emails will not be sent out.