InDesign/Digital publishing help?

I am a beginner at creating digital publishing documents/ePubs/Ebooks. My original idea for a project I have was to create an interactive PDF with simple hyperlinks and an editable form. This would be used on mobile devices such as iPhones and also tablets like an iPad. I was struggling to work out what size to create the document in, ideally I wanted something responsive to fit both mobile devices and tablets and came across ePubs/ebooks as a possible way to do that. Is that correct?

The end result of what I’m trying to achieve should be like a magazine. Rich in imagery and visual content, maybe some video content if this supports it. Should I be creating the book in two formats (one for mobile and one for tablet)? Is there some sort of best practice when it comes to this sort of thing? What about alternate layouts and using Folio Builder (something that came up on my search)?

Any guidance/advice much appreciated.

Read more: InDesign/Digital publishing help?