The characters, yeah, but they're avoiding any superpowers and going for a more grounded, Nolanesque tone, to all indications. And don't hold your breath for any boxing-glove arrows. This (Green) Arrow kills. (Which strikes me as being unrealistic in the othe direction, since most arrow wounds would be survivable unless they hit a major artery and the victim bled out before the ambulance came.)
Yes, they're going for a Nolanesque approach, but they're not going as far as Mike Grell's run in the comic books. In Grell's run Green Arrow killed, eschewed trick arrows, stopping wearing a mask after the first few issues, and there were almost no appearances by traditional comic book villains at all. So the TV show is downplaying comic booky elements, but not "as much as possible".
As for Green Arrow's ability to kill with a bow and arrow, he's skilled enough that he can make a kill shot if he so chooses. He's just that good. Whether that's realistic in the real world I don't know, but that's the way it is in Green Arrow's world.