Here is a video post by ID:
https://www.dropbox.com/s/supgzw1lhsbk5nc/by-id.jpg

Here is a video post by EMBED:
https://www.dropbox.com/s/hygreiqh9izf697/by-embed.jpg

It’s the same with your demo on themeforest, your youtube video has black sidebars on the left and right side… if you change it to embed code instead of id of the video, there will be no black bars and the video will display properly.

And yes, it displays properly in all responsive breakpoints.