Is Manjaro good for web and mobile developer? Currently I'm using Kubuntu, but I'm thinking about switching to Manjaro with i3. I'm using Andoroid Studion, Intellij, VS Code, GoLang and Java. I might replace VS Code with Vim later down the line.

I think the only real difference between distributions for web development stand point is default package repositories. And I would bet that you get more up-to-date packages on Arch (Manjaro) than Ubuntu (Kubuntu).

Manjaro is cool. The only issue you might ever run into is AUR packages breaking after running pacman -Syu, but:
- You'll notice
- You can easily look up which package from AUR needs to be rebuilt (either by missing library names or by missing app :P
For instance, I had to rebuild ffmpeg-full-git after chromium complained about some .so regarding H265 being gone.

Also if you don't use AUR packages, you don't usually run into that issue.