Traditional: 菸 vs. 煙? My IME always suggests both 菸 and 煙 for traditional 烟, which makes me think that they're interchangeable. Characters usually are not just simply exchangeable between themselves though. 

What nuances exist between 菸 and 煙?
As @YuiTo Cheng 's link

煙:


The gas produced when a substance burns. Examples: cooking smoke,soot.
The black ash condensed by the smoke produced by the burning of things which is often used to make ink.
Moisture, like water between mountains and rivers. Examples : clouds,  smoke.
Especially opium. Examples: opium smoke.


菸:


A plant name. Solanaceae, an annual herb. Its leaf is the material for making cigarettes.



Conclusion:

&nbsp;&nbsp;&nbsp;&nbsp;Related to tobacco, use "菸"

&nbsp;&nbsp;&nbsp;&nbsp;Such as: cigarettes, tobacco, tobacco leaves, tobacco wine. "香菸、菸草、菸葉、菸酒"

&nbsp;&nbsp;&nbsp;&nbsp;Related to opium and drugs, or burning something without cigarette, use "煙"

&nbsp;&nbsp;&nbsp;&nbsp;Such as: smoking halls, smoke ghosts, smoke poisons, clouds.
"煙館、煙鬼、煙毒、雲煙"