Hi,
In Windows the inputs of an audio interface are always recognized as stereo pairs.
With some devices you can make the pair to be set as a 1 channel in Windows audio settings, so that both inputs are merged into a mono signal, but I don’t remember if this is possible on Steinberg interfaces. In this case the only option available is 2 channel.
I think the easiest way in your case (since OBS / Streamlabs can host VST plugins) is to install Cubase AI that comes with your interface (or any software that can load VST plugins) and use it in conjunction with Sonobus.
Simply put a Sonobus instance on each Mic input channel, and one instance in OBS, connect them together and mute the senders on both mics instances so they don’t feedback into each other.
Many other methods have been discussed on the following topic :