Typescript is super easy to bring into a project. Just rename .js to .ts and turn the validations off. Any valid JS is also valid TS. Build step is one command to run tsc. You can turn things on slowly as you refactor into idiomatic typescript.

React is a PITA to setup and learn, as is Angular. They're the modern equivalent of Java EE. "Heavy" but if you have something complex to do and know your way around they make hard things easy. The learning curve is tough but so worth it