Yes, it is slow. But you can tweak the webpack configs to improve it. If I would work on a large project, I would probably use webpack-dev-server to serve the /client, /physics and /stats over it, instead to serve it over the node server like in production. This will retranspile the code and restart the browser immediately. Also I would configure the /server to retranspile and restart via nodemon, only if a file needed by the server has changed. This will make development much easier.
Only for readability. You could of course merge them.
Yes, it is worth it! Since you can use ESNext syntax or TypeScript. Btw I’m using TypeScript in this project.
Please take a look at a starter template. It uses webpack and does a lot of work for you. You will see that it opens many new possibilities and it is just much easier to develop with it.