Jake Bresnehan

This plugin provides you an easy quick way to test your content looks good at various sizes.
Features of the plugin include:
<ul>
<li>Mobile view</li>
<li>Tablet view</li>
</ul>
Getting setup with the plugin
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/bXe5_BvvtxA?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>
<a href="http://web-design-weekly.com/support/" rel="nofollow ugc">Plugin Support & Feature requests</a>.

Responsive Post Preview

Adds the ability to view your posts and pages at different viewport sizes with a click of a button

Rickard Andersson

macsolve

This plugin will add a grid of images in the regular WordPress editor used for writing posts or pages. Just click the image that you want to add to your post and drag it into the editor. You can drop it exactly where you want it and the plugin will insert an image with the size that you’ve chosen. It’s really simple and will be really helpful if you’re using lots of images in your posts or pages.
This plugin is developed and maintained by the Swedish company Montania System AB. To get in touch with us send an e-mail to info at montania.se or visit our web site http://www.montania.se/ (mostly in Swedish)
Browser support: Chrome, Firefox, IE7 (partial), IE8, IE9
NOTE: This plugin doesn’t seem to work in the Opera web browser. The meta box will not show up if you’re using Opera.
Translations: 
* Swedish (Montania) 
* Romanian (Web Geek Science)

ImageDrop

Add images to your posts or pages with a more user friendly drag and drop interface.

Responsive Post Preview vs ImageDrop