Hello Susanne,

I am sorry for the late reply.
I am not sure if I understand you well, what do you mean by

They seem to be referencing/echoing database fields

Actually, they are using language strings to display the text. For example, in this file: \components\com_easysocial\themes\wireframe\emails\html\registration\approvals.php you can see it echos:

<div style="margin-bottom:15px;">

    <div style="font-family:Arial;font-size:32px;font-weight:normal;color:#333;display:block; margin: 4px 0">

        <?php echo JText::_( 'COM_EASYSOCIAL_EMAILS_REGISTRATION_HEADING' ); ?>

    </div>

    <div style="font-size:12px; color: #798796;font-weight:normal">

        <?php echo JText::_( 'COM_EASYSOCIAL_EMAILS_REGISTRATION_SUBHEADING' ); ?>

    </div>

</div>

You can find this language string COM_EASYSOCIAL_EMAILS_REGISTRATION_HEADING in your site: \language\en-GB\en-GB.com_easysocial.ini which will displayed: "Welcome On Board!". All the language string will be in the language file. If you want to make a language override, you can use Joomla feature to do this. You can configure this at: Joomla > Extension > Language Manager > Overrides. Here my screenshot: http://screencast.com/t/TvFZ7E6LXbs . Or you can install the language in Joomla > Components > EasySocial > Language > (language) > Install. If you have anymore question, please don't hesitate to ask us.

Hope this will help.
Thanks.