More here: https://achromatic.dev/docs/tech-stack
Choice had a big impact, because I don't have to context switch, only have to implement validation once, can re-use a lot of the logic between frontend and backend and the UI part also looks neat. Furthermore with React server components and server actions a lot of the boilerplate code for an internal API is just.. gone. Super easy.
Now with Next.js 15 RC 2 and stable coming out next Friday, I'm in a very good position. Using the app router with Next.js 13 or Next.js 14 was like having warts. But now with Next.js 15 caching is good again and the speed improvements for dev mode were good enough to not bother me anymore.