So to summarize for most document types, print, presentations and social media, select Width & Height. For websites choose the Width only option.
What are ALL the steps needed to get this to work like in the video? They have multiple variants to get it to resize, but how many?

testing this with a New> Web page 960 px, Export website in xaras browser, not working, tested in Firefox browser, not resizing.
1) design website, Auto Fit all Objects
2) create variant(main) and (mobile)
3) the mobile pops on when scaled down, but there is nothing smooth about it.

[QUOTE]Automatic page width adjustment The new Scale to Fit Width option automatically scales content within each web variant so that it fits the width of the screen or browser, meaning your website can be viewed better on different devices.

Read more: https://www.magix.com/us/photo-graph.../new-features/