Allow multiple settings to be stored in a single option in Theme customizer

In your example here, the option stored would be named options and it would contain two array keys, toggle_header and background. To obtain the values, then, you would do:

$options = get_option( 'options', array() );
$options = array_merge( array( 'toggle_hedaer' => true, 'background' => 'normal' ), $options );

// Accessing stored values here:
$toggle_header = $options['toggle_hedaer'];
$background = $options['background'];

Naturally you should choose an ID base for the setting to be different from “options”.