Turning on Unit Specific Language is the cheapest upgrade you can give to a 14-year-old game. It doesn't cost money, it doesn't require a beefy GPU, and it fixes the single biggest immersion breaker in the vanilla experience.
Related search suggestions provided.
For factions like Sweden, Poland, or the Ottoman Empire, the default voices are often recycled. empire total war language settings better
For the smoothest experience use the Steam language selector (or reinstall with the correct language) and keep mods matched to that language. Back up saves before making changes. Turning on Unit Specific Language is the cheapest