Kevin Langley Jr.

Add widgets on a post by post basis by using a new interface directly on the post edit screen.
Filter to set the post types the Post Widgets plugin should load on post_widget_post_types

Voce Post Widgets

A better interface for managing your widgets.

Trevor Anderson

Split sidebars and widget areas into responsive columns.
Two simple widgets are provided, “Layout: New Column” and “Layout: New Column on New Row”.
Simply place these in your widget area where you’d like to create a new column (split) or new row of columns.
Gutter size and responsive collapse options are available in the Customizer -> Widget Columns panel.

Tuxedo Responsive Widget Columns

Just tested this plugin, and it works exactly as I hoped for. I can now have complex layouts in any widget areas. 
Of course it's best used for horizontal widget areas like footers, etc...



Works perfectly!

Split sidebars and widget areas into responsive columns.

Voce Post Widgets vs Tuxedo Responsive Widget Columns