The difference between ".js" and ".jsx" in a React project is mainly a matter of convention. Both can contain JavaScript and JSX code. Using .jsx makes it clearer that the file contains JSX code, and may help with syntax highlighting and code formatting in some editors. However, using .js is simpler and more common, and does not require any special configuration.
In my organisation, the ES-Lint is configured in such a way that it throws errors if we use .js instead of .jsx for components.
It ultimately comes down to your team's preference and conventions followed.