In "other" mmopg you were able to attack and kill opponents in a break deal of their own worlds. Does this happen here or is it strictly relegated to the PvP zones and arena?
I don't understand what you mean by "in a break deal of their own worlds"
I'm guessing, based off the context of your post, that you would like to know if there is open world pvp? if so the answer is yes, but you need to roll on a pvp server (or the one and only RP-PVP server).
If you are on a pve server, you may manually flag yourself for open world pvp (click on your portrait and select flag yourself) but you can't attack other players who didn't flag. If you are flagged and they are not, they can attack you to initiate the pvp. That will result in them getting auto-flagged, but they will always get the jump on you in that scenario. So roll on a pvp server if open world pvp is your thing.