The official description says: “Bounty Worlds are basically a mix of 3 previous PvP games. It has the best bits we can reuse from Bounty Hunter, PvP worlds, and the old Wilderness. In short, we’ve increased the chance to get your opponent’s items and we added the thrill of hunting a bounty within the Wilderness while surrounded by hundreds of potential PKers.”
In other words, in these new Runescape worlds you can attack anybody within the level range – if you kill somebody who’s not a target, it will be considered a “rogue kill”, but there will no longer be score penalties for these. Instead, it will add 1 point to your rogue kill highscore and you will get a drop that’s very likely to be one of the items the target was carrying. So it really is not worth killing low level players!
However, if you go for your assigned target that will be of a similar level with you, you will receive a generous boost to your drop (if you defeat the target, of course).
But it’s not all about the rewards with this new Bounty Worlds update for Runescape! It’s more about the balance and the thrill of actually hunting down somebody your “own size” rather than taking advantage of your strength against lower level characters. Because, in the end, that’s what a MMO should be about: balance and not “who can spend more time in the game’s world to get to a higher level”.