Auto scale advices

Hey everyone!
Thanks to COVID-19 I’ve got not easy task to build video conference solution that could handle more than 200k users (400k streams) simultaneously in the peak hours. I’ve made my research and I’ve selected Jitsi for this use case.
The planned architecture so far is:
-load balancer with autocaling (Jitsi meet/nginx) images
-behind them I think to put the same thing but with Jitsi videobridge.

My questions are:
-What should I explicitly look at for such configuration and load?
-What would be the bandwidth for something like this?
-Which would be better for this scenario (AWS or GCP) ?
-In your experience what would cost simultaneous stream for 200k users (400k streams) per hour?
-Do you have better idea for this solution?

Thanks a lot in advance for your answers!