Hi, Stephen. Thanks for your detailed request.
Finding things via the REST API is resourceful (so kudos!) but not the best way unless you’re talking from SiteA to SiteB. Within a single site, you should just use PHP.
Our plugins utilize WordPress standards (custom post types and postmeta).
To get the email for an Organizer with Post ID 281, you would do this:
$email = get_post_meta( 281, '_OrganizerEmail', true );
Once you have that, you might want to run it through sanitize_email() and then pass it to some part of wp_mail() — or just display it somewhere.
Hopefully this helps!
Please let me know how this goes for you.