Modal windows/dialog (AKA pop-ups) are great and provide a great experience for the end user - they allow for a quick display of content in an overlay without navigating to another page. Fortunately, it’s relatively straightforward to implement in Drupal 8.
Here's how to do it with an entity builder callback without any additional contrib module like "Automatic Entity Label" or "Automatic Nodetitles", using only Drupal core functionality.
You can make YouTube videos responsive with CSS. Wrap the iframe in a div with the class of "youtube-container" and apply the styles.
Here is a very quick and simple example of how to create an administrator on any drupal 7 website.
The example which shows how to build a nice chart using a minimum of JS code written.