This is how to setup Voicemod with Streamlabs:
From Streamlabs OBS you have to create scenes by selecting video sources (webcam, capture input, PC desktop, etc.) and audio sources (stream microphone, Voicemod virtual cable output, etc.).
In this way it is possible to have scenes in which the original signal of the mic is used and others in which the audio signal processed by Voicemod can be used.
Sample of Input of the Gaming PC + Micro streaming + Webcam
Sample of Input of the Gaming PC + Voicemod + Webcam