Setting and enforcing default web browser

You should look into using Enterprise Mode to address website compatibility issues. These allow you to specify which websites open in IE to address compatibility issues. You also have the option of sending all intranet sites to IE via GPO.

Have a look at this blog post to see what you can do to manage file associations from an enterprise level: https://blogs.technet.microsoft.com/windowsinternals/2017/10/25/windows-10-how-to-configure-file-associations-for-it-pros/