With JomSocial's 'Use SourceCoast's JFBC' option, the social buttons are inserted by JomSocial in their pages. If you want to put the social login buttons in a different position on the page, then you'll need to change JomSocial's code for the registration view.
It looks like the printing out of these buttons is in /components/com_community/templates/jomsocial/layouts/register/base.php with the following block of code.
<?php if ( $fbHtml ) { ?>
<div class="joms-form__group">
<span></span>
<?php echo $fbHtml;?>
</div>
<?php } ?>
Change social links location on Registartion form
