I'm an old php dev, still doing server side development exclusively, and these are genuine questions:
1. What tooling is there available? Do you mean something along the lines of vim or IntelliJ?
2. How do these techniques make the user experience better, compared to e.g. ajax?
So here's the thing about the JS world: You have access to essentially all the tooling ever developed for frontend dev. Linters, code formatters, IDEs, etc. Tons of crazy techniques invented to speed up development (hot-reloading in various frameworks; remote debugging with the various browser inspectors…).
All this becomes available to your server development experience the moment you choose to share the language. And having developed with Python for over a decade, I can safely say I no longer enjoy doing that after seriously using typescript for just under a year. This also does have to do with the IDE; VSCode with TypeScript is a better dev experience than Python with any of the popular Python IDEs, even with added typings (python types are awful).
> 2. How do these techniques make the user experience better, compared to e.g. ajax?
They don't. They do enable you to take advantage of them in order to make a better user experience, but you still have to actively pursue that. Someone gave the example of Reddit lower down which is possibly the worst SPA I've ever seen on a popular site. OTOH, if you look at well-built NextJS websites, they're often ridiculously fast both to load and to use.
