https://news.ycombinator.com/item?id=19131272 . It don't know where your 2% number is coming from, but in Airbnb's experience it was much more. It feel like it would also be more, imo, but I guess it depe nds.

Typescript can be annoying but usually it helps a lot with refactoring. It's also pretty great for detecting unused props with react.

I don't use IDEs so my defense of typescript is only based on its type checking merits