We’ve definitely heard the request for whitelisting, but it’s not something we can do at this time. I will definitely post here on the dev forums if that becomes a possibility.
The theme used is determined solely by the embed parameters, but this is something you could configure if you’re storing session states / persisting preferences for your users!
As for the “Stream Chat” banner, this indicates that the chat embed is showing the stream’s chat, rather than one of the rooms that the broadcaster may have created. Rooms chat is something we’re open to adding support for in the embeds if it’s something folks find valuable.
I hope this helps! Happy to answer any follow-up questions as well.