I used to smoke
As you correctly say, this "used" is usually used to to refer to actions that happened in the past which don't happen now.
I used to be able to dunk when I was 20. I can barely jump at all now, and it has been like that ever since I tore my ACL.
I smoked before.
does not necessarily mean that it was happening in the past and don't happen anymore.
I smoked before. What? You smoked before coming to the party? What did I tell you about that?
"Before" does not have any connotation of "not happening any longer in the present." But the use of other relevant words can help mean that.
Before I met you, I was an addict. You changed my life around.
Here, "met" is what stops the timeline of being an addict.
I smoked earlier.
This is even more lose and vague than using "before". It has the same problem as the one earlier. In fact, "earlier" by itself is almost never used in a sentence to say that something only happened in the past and that it does not happen now anymore. You can use "earlier" to mean something like that but it will need to be phrased with other helping words to form that context.
Example: "Earlier in my days, I would play almost every sport in the university. Now I am more selective and focus on only basketball."
Here, using "earlier" makes sense as it is supported by "in my days" and "would" which means "used to".