Project with 2 way sound

Hi all.
I like to sent live speak/sound from the mic on the soundblaster USB card to the dashbord on my iphone. And on my iphone send/talk to the other end.
If possible i like to chose between two sound cards on the pi. Same as it works in two room?
I hope someone can help me with this.

Why Node-RED? Any particular reason?

Yes i control a lot of other stuff in NR dashboard so I cant switch app or browser

Hi i use this and work fine (need https on node-red server > mic access)

Voice Intercom Websockets (flow) - Node-RED (nodered.org)

I just tryed this. But I have some questions.
I have npm on the pi do I need to install anything else.
Do I need to make the Firebase project also?? and follow everything in this link Firebase + WebRTC Codelab

Do you think it is possible just to stream the sound from the camera mic directly from this flow to the dashboard on my iphone you think.

And i need to send the speak from the iphone to the speaker on the PI. But this should the flow also do right??? I just cant get it to work.
Can/will you help me, please.....

Hi,
just a pi nodejs and node-red
A camera with a mic and pi node and audio node for NR
This flow need a touchscreen to Push To Talk it s a bidirectionnel talkie walkie not a babyphone

Thanks for info.
Is it possible you can help me because i like to have a function so I can remotely turn on the mic in a escape room an listen to the guest.
And the i like to talk to them also. So all talk have to be controlled from the phone. So it is not the walkie talkie concept that fit to my setup.