There are few different ways. In general, below approaches are popular.
1. Use Style System: Use this approach, If you want to provide a authoring capability for authors to select the style system: https://docs.adobe.com/content/help/en/experience-manager-65/developing/components/style-system.html
2. Use HTML Attributes/CSS Selectors: Sometimes, we want to roll some styles globally on specific languages. This is most common use can you can use HTML attributes to define the styles specific to a language/locale.
Ex:
html:lang(ja) {
font-family: "Arial",Helvetica;
}
All the languages pages would have either the lang attribute or some other attributes to tell the search engines that the page belongs to a specific language. So, you can use that along with the CSS selectors to define the styles.
Thanks,
Singaiah