Yes, no, maybe, no, no, yes, yes..... Just kidding!
The lounge is all self service. In theory you can take all you want, but the plates are tiny and you would really have to be talented to fit a lot on them. It's my understanding the water is in large glass bottles, but you are able to ask for one or two to take back to your room. (You could pour into something else to take to the pool). Yes, you can bring stuff back to the room on trays, and yes people definitely share tables. We have met some very interesting people from across the globe in the Poly lounge!
Our last trip was in 2000 (headed "home" in August) so someone who has been more recently please make corrections to my info if necessary!
Hope this helps!!