Note that I stated "Stereo Mix" is not recommended as input for speech recognition, specifically, as it'll cause the speech recognition engine to hear all audio (including music, ingame sounds, etc...), which it'll try to recognize as speech, in addition to having to try and pick up your actual speech out from all that (similar to using a sensitive desktop microphone with speakers, but even worse).
That said, for playing back specific sounds to an input device, using stereo mix isn't ideal either, as the ingame sound (and anything else playing at that time, like music) will be heard in addition to the sound you're explicitly playing.
VB-CABLE by itself won't facilitate routing your microphone audio to the input device; You'll need something like "Voicemeeter" for that.