Custom Page that comes with preloaded content for the user

You can do this like this: (answering from mobile. Please forgive if the markup is broken)

add_filter( 'default_content', 'preloaded_editor_content', 10, 2 );

function preloaded_editor_content( $content, $post ) {

    switch( $post->post_type ) {
        case 'your_post_type':
            $content="your content";
        break;
        default:
            $content="your default content";
        break;
    }

    return $content;
}