You will need to provide a bit more detail, I suspect. I have no idea what you mean by watching 'USB streaming live'
Realize that OBS Studio is designed as a compositing tool, that is - compose a single video output (Record and/or Stream) made of up multiple sources (one or more video inputs, one or more audio inputs, overlays, etc).
USB is a digital connection protocol... not something to 'watch'
There are USB connected cameras, capture devices, etc. In which case there is video going over USB (or could be HDMI, NDI, SDI, etc).
In recent years, OBS Studio added a Presentation Mode feature to output a display view of what is being composited (ie the Stream/Recording output). OBS Studio can Stream and Record at some time. Streaming is designed to use industry standard protocols, and you can point streaming to most any Stream Ingest (Receiver) server, including your own (... but that is NOT a common, consumer friendly, setup).
So, you need to clarify
- do you simply watch to watch real-time what you are recording? if yes, why does the OBS Preview window not suffice in your situation? A common reason for user frustration is only having a single monitor. Dual monitor (or large monitor) can do wonders for one's workflow
- or you want to watch on another display on same computer? refer to OBS Studio Presentation Mode
- you want to watch on another device entirely... that gets a bit more complicated, and depends on exact device(s), their specific operating system and capabilities, etc. This could be relatively easy (NDI output from OBS Studio to another network device with NDI listener, to Presentation Mode output, HDMI capture device re-routing over network, to stuff more complex depending on target device(s), quantity, etc)