There have been several requests to include the Program Audio with the Virtual Camera or Fullscreen Projector, either tied directly together or as a separate physical/virtual audio device that can go to the overflow room of a live event or get picked up by another app like an online meeting. But so far none of that has happened yet.
If you want a physical or virtual audio out that isn't tied to a stream, you'll have to use the Monitor...which has its own problems because whoever wrote that decided to expand the buffer to infinity instead of resampling to stay in sync. If you connect the Monitor to something that has the same clock as OBS does, then you're fine, but if you connect it to something that has a different clock, even with the same nominal setting, then it slowly drifts out of sync until it becomes useless, with a huge buffer.
So an internal loopback is probably fine, like VB Cable or Voicemeeter, but an external sound card (speakers or headphones) is a mixed bag. Some work, others don't. One possible workaround is to send the Monitor to Voicemeeter, for the sole purpose of bouncing it from there to something physical, because VM does resample.
