Regarding NPCs there are two possibilities depending on the DDA version you’re using. In the data folder of your DDA install there is either:
A) 1-2 files called no_npc.txt and/or nonpc.txt - delete both to activate NPCs.
B) A single file called npc.txt - edit it in a real text editor and change the ‘n’ after the two options at the bottom to ‘y’.
Both possibilities mean you’ll need to generate a new world - no save compatibility.
For Smokers you’ll need to dig into the source code, deactivate them, and recompile. Alternately you can try Classic Zombie Mode, but this removes all special zombies and many other features - like labs and temples.