When you import an ElevenLabs voice into Speechless (https://app.speechless.games/import-ai-voices), it is assigned the “ElevenLabs Multilingual V2” model by default.
You can switch to V3 later if you wish. To do this, go to the voice’s page (from https://app.speechless.games/ai-voices), select the model, and save your changes.

This option is only available for voices you have imported yourself, not for Speechless’s predefined voices.

Note: V3 is still in alpha and may change according to ElevenLabs.