Get the featured image of an ACF relationship field

According to ACF documentation, a foreach loop is to be used to access the items in a Relationship field.

Untested:

$templates = get_field( 'field_61318c078a746' );

foreach ( $templates as $template ) {
    $template_image_id  = absint( get_field( 'Image', $template ) );
    $template_image_url="https://example.com/fallback-image.jpg";

    if ( ! empty( $template_image_id ) ) {
        $template_image_url = wp_get_attachment_image_url( $template_image_id, 'large' );
    }

    ...
}

In most use cases you will not need to interact with field groups on the frontend. There are occasions for it, but very few in my experience.