JetBrains has unfortunately not prioritized settings sync. There are plugims for doing this, but they frequently corrupt your settings, especially across the different JetBrains editors.

For style consistency, JetBrains does natively support EditorConfig, I would check in a .editorconfig at the root of each of your git repositories.

For specific programming languages, there also also some plugins that interact with version controllable style settings, such as Checkstyle and ESLint

I'm using already Checkstyle, but some stuff like Copyright header and live templates are hard to sync and each dev has its own editor style (theme, Font), so the repository setting is not a viable option

This is a better question for Jetbrains than for HN. The vast majority of devs will have internet access while working, so you’re in a tiny minority.

On that note — how do you even work without internet access?

With transient server which cache all the dependencies (e.g. Nexus, private Docker Registry, Debian APT mirror)