Render template for HtmlResponse In my controller I want to return Drupal\Core\Render\HtmlResponse, and also I want to take HTML content from the template. The problem is that if I will try to render() a rendereable array before returning HtmlResponse - I'm getting "The website encountered an unexpected error. Please try again later." error. Array is being rendered correctly when I will just return it as it is, but with all Drupal HTML, which I don't want. What am I doing wrong?

Added #1: Discovery - all works well when I return Zend\Diactoros\Response\HtmlResponse . Now I'm even more confused. Why is that?

Added #2: When I use "renderPlain()" renderers method it also works, but I'm not sure of drawbacks yet.
Oh, I believe I should use "renderRoot()" method of renderer in case where I'm rendering HTML for response just to be send. Please correct me someone if I'm wrong.