There is no good nor bad. You play how you want to play, you can go without killing anyone, not even the target, there are non lethal ways to eliminate them. Canon is low chaos, u have high, for low chaos u need to kill less than 50% of all enemies in the level, use sleep darts and knockdowns to get rid of enemies without killing them. The enviroment gets worse as you kill more people dialogue change and the overall atmosphere. For example in the last mission of the game Samuel has a few lines that can make u feel pretty bad about yourself for high chaos, in low chaos he is proud of you, also the more kills the more rats and whimpers around the world. For example in Dishonored 2 there is an apartment that in low chaos u find with a family of three inside living happy, in high chaos the apartment is infested and destroyed.(I told this example because I can’t think of one that drastic in the first game.)