I don't know if Adobe has ready some videos so people can see the new features of Adobe Muse CC 2018 in action?
I am very interested to know how the new form widget works?
As far as I know the new form widget allows you to add unlimited custom fields and check radio buttons.
How may I learn how to use the new form widget in Muse CC 2018?
As of now I can help you with this doc - Add contact forms and style form widgets in Adobe Muse, which will give you a detailed overview of responsive forms in Muse.
You can find more updated videos here - Adobe Muse tutorials | Learn how to use Adobe Muse CC
Hope this helps.