On the One you bring up the second screen by holding a button. As you can't move around while using it its effectively the same as physically holding the second screen.
At no point has there ever been a scare whilst rummaging through the backpack. Tbh you never really need to look in it, though. You're tooled up with a cricket bat and there's rarely more than one or two zombies in a room, and they move too slowly to touch you (and would have to hit you about ten times to kill you). Why open your backpack?
On the rare occasion I do open it, though, it's when I know there are no zombies around. Since you can see them a mile off and you have a permanent radar pinging anything that moves it's impossible to get surprised by an npc.
Level design is okay for a game with such small set areas, but all in all is one of the weakest parts of a game that has a great many weak parts. Why isn't it open world? It should at the very least have several choices in routes you take. Way too linear for my taste.
Lighting is pretty dire. Everywhere is either brightly lit or pitch black. Walk down a corridor between those extremes and its not a gradual thing - you're in light then you're in darkness. But it doesn't matter because you have a torch that you just leave turned on all the time. (You'll occasionally need to stand still somewhere for a minute to let it recharge, but that's fine as you can do it anywhere. It can be pitch black when your torch runs out but if you just stand still when it does you'll be perfectly fine until it recharges.)
It's the lack of skins that really irritates me though. I've killed the same six or seven zombies twenty times each, and each in the exact same way. No matter where you hit them, the top right of their head always goes on the first hit, whether you're using melee weapon, crossbow, gun, whatever, then nothing changes on the next five hits, then their head explodes on the seventh.