Joel

This is an extremely simple plugin (one line of code!) that deletes all domain cookies whenever a user logs out of your WordPress site, and then redirects the user to the site homepage.
Why? Because by default, WordPress sets a number of cookies that it doesn’t remove on its own when you log out.
There are security and privacy benefits, because if there are vulnerabilities in WordPress or in your browser, or if someone has access to your computer or device, they may be able to access these cookies. (That goes for you or for anyone who logs into your site to add a post or comment.)
Likewise, when a user logs out of your site using a public or shared computer, there won’t be any domain cookies left behind.
The plugin also gives you back the “regular user view” of your site, because after you log out you can browse your site as an anonymous user, without having to manually clear cookies in your browser. (There are many plugins that will display different content or show cached or uncached versions of pages if they see that WordPress cookies have been set.)

Logout Clear Cookies

Clears all domain cookies on logout. Because leaving a trail of cookies is bad.

ema-digital

This plugin enhances user privacy for embedded YouTube videos by serving videos from 
the youtube-nocookie.com domain.
YouTube videos that are embedded in the editor by the standard <code>iframe</code> tag, 
oEmbed, or short tag will be automatically converted to use the enhanced privacy 
feature. YouTube videos that are embedded in widget areas using the <code>iframe</code> method 
will also be converted to the nocookie version.

EU Tube User Privacy

Enhances user privacy for embedded YouTube videos.

Logout Clear Cookies vs EU Tube User Privacy