Wordpress theme edition with Bootstrap

Question

some questions. I am studying Child Theme because I was told that is the best way to change topics.

Question:

I’m doing a lot with bootstrap and would like to change a theme that has bootstrap, in case I won’t use the style.css because I want to add bootstrap things to the page. How should I proceed?

Solution proposal:

Copy and paste the index.php of the parent and colo theme into the child theme and change the parts I want to change? That’s correct?

Another possible doubt:

How would the administrative part work? I need to edit the banner, for example. Maybe also a text from one of the three columns below the banner. The simplest solution would be to use a plugin? The question is whether it will work perfectly with Bootstrap or will it have conflicts? It is a good practice?

Reason for the question:

I am looking for the best current solutions and practices.