They are similar.
Google Fire does what it can, automatically. But there's no much room for customization, for building a CLI the way you want it. Google Fire can build a CLI from objects like dicts, lists, classes. Typer only with functions, but allows you to customize the CLI.
Fire would be great for quick hacks. Typer for CLI programs that you want to use more than a couple of times.
Also, more similar to Fire is Typer CLI https://typer.tiangolo.com/typer-cli/ , that will give you a CLI for any Python file with a function (with or without Typer), with shell completion in all the shells. And that one doesn't even need you to import another library (like Fire or Typer).
