Most of the names you can find by looking at the Git history of Element’s repos - but that seems a bit stalkerish to people that have private lives to me.

The error shown in the video is the one that means that they just… didn’t set up video calling? It requires more setup than just the text chat for technical reasons that no service can escape.

Resource usage is a common complaint for Synapse hosters, you might find something like Continuwuity more lightweight