If you use type-to-speak, the voice you choose is what the other person hears when your typed messages are spoken into the call.

Go to Settings → Voice and choose Female, Male, or Neutral. These are the same voice options available in Rylo Phone, so if you've already picked a voice there, you'll hear the same one on Sidekick.

Yes - each option in Settings plays a short sample so you can hear it before deciding.