A responsive design should respond to the screen size or shape in the way the designer intended, but this doesn't give the user the choice to select the features that they want.

Resizeable allows the app designer to give the user some ability to make the decisions about the relative sizes of elements in an app or a web page.

CSS can be used to allow the resize of a elements in Firefox, Chrome and Safarai, but not IE or Edge ( March 2018)

A range input can be used to control the size of elements, with the help of a little Javascript. This works well in Firefox and Chrome.

JQuery allows multiple elements to be resized at the same time, and is much more browser compatible.