Chest drops help

I heard someone saying you can see what's the going to drop before its opened at the raid, like you can see which one is going to drop potions and which is going to drop ring. I'm not asking the drop table on ML HC and HG HC raid chests, I just want to know if there is a way to see which chest there is going to drop the rare item.

And there are players who can open all boxes at the same time. The world bosses also beat up faster than usual (it can't actually go that fast)

cringe randoms