We have a plethora of default voices available to you, and you will find an even larger number of voices available to you via the Voice Library.
One thing to keep in mind is that all of these voices are English. This means that if you plan on using these voices for languages other than English, they might have a slight English accent. Unfortunately, there is currently no way to change this.
The way to get a voice with a proper accent for the language you want the AI to speak is to clone a voice speaking the language with the proper accent.
You can find a few voices in the Voice Library under the professional category (they have the golden check mark) which are cloned voices of real people, and some of those have different language tags, which means that they have been cloned in a different language.