Cameron Jones

Fluid Customizer is a simple plug-and-play plugin which allows you to resize the width of the preview window in the Customizer to whichever size you like. Simply install the plugin, go to your Customizer, then click and drag the right border of the sidebar and watch the magic happen!

Fluid Customizer

Preview your site for a variety of different devices by resizing your Customizer sidebar with a simple click and drag

Dojo Digital

This plugin adds a textarea to the Customize page that allows theme editors to write, preview, and implement CSS code in real time. 
It also includes a frontend CSS editor window with live preview capability.

Live CSS Preview

Live front-end and Customizer CSS editing powered by native WordPress Additional CSS storage.

Fluid Customizer vs Live CSS Preview