SetAudioOutputDevice 

Namespace: SynicSugar.RTC

public static void SetAudioOutputDevice(AudioOutputDeviceInfo deviceInfo)

Description 

Change OutputDevice.
AudioOutputDeviceInfo, ChangeOutputVolume

using System.Collections.Generic;
using SynicSugar.RTC;
using UnityEngine;
public class MicSetting : MonoBehaviour {
    public void Start(){
        List<AudioOutputDeviceInfo> outputs = RTCConfig.GetOutputDeviceInformation();
        RTCConfig.SetAudioOutputDevice(inputs[0]);
    }
}