The Simple XML Sitemap module was originally created by gbyte as a temporary replacement for the non-functioning Drupal 8 XML Sitemamp Module. After putting some more work into it however, we decided to keep using it in our D8 & D9 projects, as it is very lightweight, simple to use and most importandly, adheres to a newer XML sitemap standard.
The Drupal 7 translation system including the internationalization package is a heavy beast and while it mostly gets the job done, it is all but intuitive in use.
For high volume translations it is recommended to use the translation template extractor and translate the strings externally. For small corrections however, it is often much more convenient to use the translation interface (admin/config/regional/translate/translate).