How do I change options on custom page templates and custom post types?

To change the options on custom page templates and custom post types in your child theme's functions.php file add:

function ghostpool_custom_init_variables() {
    // Custom page template
    if ( is_page_template( 'custom-template.php' ) ) {
        $GLOBALS['ghostpool_title'] = 'gp-large-page-header';
        $GLOBALS['ghostpool_layout'] =  'gp-no-sidebar';
        $GLOBALS['ghostpool_sidebar'] = 'gp-standard-sidebar';
    }
    // Custom post type
    if ( is_singular( 'custom_post_type' ) ) {
        $GLOBALS['ghostpool_title'] = 'gp-large-page-header';
        $GLOBALS['ghostpool_layout'] =  'gp-no-sidebar';
        $GLOBALS['ghostpool_sidebar'] = 'gp-standard-sidebar';
    }
    // Attachment page
    if ( is_attachment() ) {
        $GLOBALS['ghostpool_title'] = 'gp-large-page-header';
        $GLOBALS['ghostpool_layout'] =  'gp-no-sidebar';
        $GLOBALS['ghostpool_sidebar'] = 'gp-standard-sidebar';
    }
}

Some of the option names may vary from theme to theme. You can view all the available options and the correct names in lib/inc/init-variables.php.