Bootstrap 4 and Framework 7 Usage

When I design an application I have always selected Bootstrap 4 local. This allows me the greatest flexibility for designing server-based applications from Desktop to Handhelds.

It is my understanding that if you’re designing for phones and tablets only, that you’re better of using Framework 7. And more so, if you’re designing apps. So here is my question with the 3.2.2 release of Wappler.

1. Can you use Framework 7 to design from handhelds to desktops?
2. Can you use both Bootstrap 4 local and Framework 7 on the same page design?
3. When should one only use Bootstrap 4?
4. When is it best to use Framework 7?

I look forward to hearing your opinions. Thank you in advance.