Your choice. Wolfhounds can be avoided or dispatched with sleep darts rather than killed, and there's a contract to kill and cremate one, but it's completely optional.
In the last part of the final mission, there are some really nerve-wracking enemies with a very wide range of detection who can teleport to you out of seemingly nowhere. They can't be killed stealthily and are hard to avoid.
There's no chaos system like in the other Dishonored games, and you can choose the ending regardless of playstyle. One is more optimistic than the other (it's obvious which), but both are somewhat bittersweet.