LOTS of discussions of this (remote guests) in recent years.
There are NUMEROUS options, each with its own Pro's & Con's (including costs, technical difficulty to setup and operate/maintain, reliability/maturity of solution, etc). Depends on budget, technical expertise, other in use technology (ex if using NDI already for video feeds, ex PTZ camera, using NDI Bridge might make sense)
And yea, obviously looping audio will be an issue you have to design around (easy to do, though not always convenient). Unfortunately for you, a lot of the echo cancellation techniques vendors use in various applications aren't compatible with the Free, Open-Source nature of OBS Studio (meaning you'd have to come up with your own solution, whether in software or by audio design (make sure your in-house podcast hosts aren't listening to guest via speakers picked up by their microphones (ie, an audio loop). This is why you often see Hosts using headphones. Another option would be running audio through an external sound system that can do the echo cancellation for you, and feeding that into OBS Studio computer). I'm no sound engineer, and definitely NOT my area of expertise. but the quick and dirty, cheap solution is for Hosts and Guest to use headphones (even if only small earbud in one ear... and go wired, not wireless).. that way each mic is ONLY picking up the speaker's voice, and nothing else
