checkout voicemeeter banana
i use it to output to 2 physical and 1 software audio devices
i also use it to handle 3 input devices, so i can talk to friends on discord without it going to my stream and friends dont turn up on my stream while still able to stream my voice with a button press
its free software, but i suggest getting the extra virtual audio cables for a few quid
iv not streamed for quite some time, but have a play with it, its hard at first but once you figure it out its very powerful