Getting array of customizer settings

Yes. You can get an array of all registered settings via $wp_customize->settings(). If you want to display them all you could do this:

if ( is_customize_preview() ) {
    global $wp_customize;
    $theme_mods = array();
    foreach ( $wp_customize->settings() as $setting ) {
        if ( 'theme_mod' === $setting->type ) {
            $theme_mods[ $setting->id ] = $setting->value();
        }
    }
    echo '<pre>' . json_encode( $theme_mods, JSON_PRETTY_PRINT ) . '</pre>';
}