I’m no expert on the higher capabilities of multistream plugins and whatnot. I don’t think you could include twitch chat with the others if you are doing that sort of thing unless filtering chats to a given platform is an option with one instance. All the same, if you are handling the multistream locally you would want to do a dual PC setup if you are a game streamer. A lot of multistreamers use a relay service to reduce processing power while gaming.

You can multistream everything to everywhere with combined chat, but you have to sanitize the chat so it isn’t apparent that other platforms are combined or which chat is which if they are displayed separately.