The binaries that ship with Indigo install their own shared libraries to /usr/local/Indigo. However there are a number of cases where they do still depend on macOS dylibs (stuff like libSystem, libiconv, libc++). In this case macOS updates won't ruin your setup, because Indigo will ship with binaries that specifically work with the new OS.

Re: 2) if that works for you that's great. However a lot of developers end up using Docker abstractions (for very good reasons) such as Lando or Laradock which specifically don't attempt to replicate a production environment any closer than Indigo does. So as @Chrischen says below, use something highly productive for development, and use a clone of your Production Docker stack for QA. Arguably that's the only way to truly be sure your tests pass in your Production environment.