In addition to the new map data, a new map rendering engine has also been implemented, This new engine is improved in all aspects. For example it has much higher hillsahding quality:

A new style has been implemented for OSM data, with better colors and less noisy textures:

It is also enabled for map style mods, and you can already find some community provided mods in the Steam Workshop to both modify the base map and to display new information in the underlying OSM database. Read the devblogs for August, September and October for all the details:
https://carloscarrasco.com/nimby-rails-august-2023/
https://carloscarrasco.com/nimby-rails-september-2023/
https://carloscarrasco.com/nimby-rails-october-2023/