It’s not exactly clear if the monitoring is before or after audio filters which is important because of their next couple additions. For your common, everyday broadcasting needs, this might be a little advanced but for larger productions of video shows or podcasts, it could be very useful.
In the advanced settings, you can now set a device to monitor your audio from.
OBS version 18.0 was released today and it adds some pretty nifty features. At the top of the list is audio monitoring.