1.) The visual difference is you don't see your complete page with master frame until preview, with master page you have WYSIWYG?
2.) With the master frame you get a more automatic placement of objects, so to speak, with the content place holder and in relation to page length?
3.) Master Frame, does the layout(bootstrap) grid work?
4.) Master Frame, does the flex box work?
5.) Master Frame, does the css flex grid work?
6.) Master Page, does the layout(bootstrap) grid work?
7.) Master Page, does the flex box work?
8.) Master Page, does the css flex grid work?
9.) When is it better to use the Master Frame or the Master Page? Does it matter? Or does that depend on the features/objects used? And, or do we need to experiment on our own.

I apologize for all the questions and I know there's been 10k posts about this, but I've been looking at this for years.
(Response does not have to be today.)
Best Regards