Alex

<blockquote>
A picture is worth a thousand words. How many words is a video worth?
</blockquote>
Featured Videos work like Featured Images, just smoother: Paste a video URL into the designated new box on the post edit screen and the video will be displayed in place of a post image.
There are three ways to get the videos onto your page:
<ol>
<li>Automagically! If your theme makes use of WordPress’ native <a href="https://codex.wordpress.org/Post_Thumbnails" rel="nofollow ugc">featured image functionality</a> you are set: Automatic insertion, lazy loading or lightbox overlays, its your choice. If this does not work you can either</li>
<li>insert the <code>[featured-video-plus]</code>–Shortcode in your posts or</li>
<li>manually make use of the PHP-functions in your theme’s source files.</li>
</ol>
For more details, check the <a href="https://wordpress.org/plugins/featured-video-plus/installation/" rel="ugc">installation</a> page.
<blockquote>
Theme compatibility 
 Sadly many themes do not follow the WordPress standards and implement their own fancy functions for displaying featured images – those very likely break this plugin. Check out the <a href="https://wordpress.org/plugins/featured-video-plus/faq/" rel="ugc">FAQ</a>. Another common problem are sliders: Videos, in general, do not like sliders at all.
</blockquote>
See the plugin in action on <a href="http://yrnxt.com/wordpress/featured-video-plus/" rel="nofollow ugc">yrnxt.com</a>. There is a button in the sidebar to switch between the different featured video display modes: <a href="http://yrnxt.com/wordpress/featured-video-plus/?setfvpmode=replace" rel="nofollow ugc">Automatic</a>, <a href="http://yrnxt.com/wordpress/featured-video-plus/?setfvpmode=dynamic" rel="nofollow ugc">lazy</a> and <a href="http://yrnxt.com/wordpress/featured-video-plus/?setfvpmode=overlay" rel="nofollow ugc">overlay</a>.
Besides Local Videos you can use videos from a whole lot of external providers like YouTube, Vimeo and Dailymotion. SoundCloud and Spotify (including playlists) are supported as well. Check the <a href="https://codex.wordpress.org/Embeds#Okay.2C_So_What_Sites_Can_I_Embed_From.3F" rel="nofollow ugc">WordPress Codex</a> for a complete list. If some provider is not listed you can always just use an embed code or whatever HTML you like.
After installing the plugin check your site’s Media Settings (<code>Settings -> Media</code> in the administration interface): The plugin adds quite some little helper options there. Change to lazy or overlay mode, tweak video sizing, individualize the look of the most prominent providers’ video players and turn on autoplay or video looping. By default videos try to dynamically fit their parent containers width and adjust their size responsively.
<blockquote>
Support 
 I do read all support questions in the <a href="https://wordpress.org/support/plugin/featured-video-plus" rel="ugc">forums</a> but cannot reply to all of them. The plugin is an unpaid side project and full support would require more time than I can invest for free for over 20k active installs. If you really need help, consider <a href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=AD8UKMQW2DMM6" rel="nofollow ugc">buying me a cookie</a> – best way to attract my attention and to support future enhancements.
</blockquote>

Featured Video Plus

Add Featured Videos to your posts and pages. Works like magic with most themes which use Featured Images. Local Media, YouTube, Vimeo and many more.

Sibin Grasic

Responsive Videos plugin will allow you to automatically resize and scale your embedded videos on mobile devices. 
CSS selector option is provided so you can target only your post / page content container.
Features
<ul>
<li>Automatic configuration option</li>
<li>Automatically resizes / scales all your embedded videos</li>
<li>Works on all browsers</li>
<li>Highly compatible – you can change the css selector for the text highlight</li>
<li>Customizable – you can select the page type on which to activate the fitVids script</li>
</ul>

Responsive videos – Fitvids

Nice one

Good

Make your Embedded videos responsive on mobile devices with jQuery FitVids plugin

Featured Video Plus vs Responsive videos – Fitvids