Choose YouTube Preview Image Resolution

If you are using the LazyLoad sub-option Replace YouTube iframe with preview image, you may use the Helper Plugin below to specify the resolution of the preview thumbnail. 

Heads up! You need to modify the plugin’s PHP file first, to specify which resolution to use.
Possible values are: default, mqdefault, sddefault, hqdefault, maxresdefault

📥   Download (.zip):  WP Rocket | YouTube Preview Image Resolution
Developers: You can find the code for this plugin on GitHub.