"Take from OBS" means just that. It takes the settings you have for OBS's built-in streaming encoder process and uses them for that stream. Of course, any others can use other settings (different profile, different bitrate, etc.), but if you say, "Take from OBS", your settings there will directly be used in that session. That's how I can simulcast to YouTube and Twitch and still have the same high quality on both streams, yet still be in compliance with (one of) Twitch's simulcasting provisos. If I had to use different quality settings in any of the streams, I would have to specify settings in the output set up in the plugin to worsen the YouTube settings. To wit, Twitch basically says, like the Ten Commandments of Streaming (should I channel Mel Brooks here?), "No other parallel stream shall be of better quality than that on me."
When it comes to chat, the other big proviso you need to observe while multistreaming, that's not something for this particular thread. That's best discussed elsewhere. ;3
--Katt. =^.^=
P.S. For the record, I'm using Sorayuki's release, which I have had zero problems with using here.