I guess the second method is less time taking and will also take overall less memory than the first method. While in first method you individually have to make sprite of each texture which is a bit hectic and time taking.
I will go for the second method if i have all the symbols in 1 texture atlas.
Edit: I was referring to the last method you mentioned i.e. third one.
I don’t think you will get much optimization improvements by having an atlas with a sprite of a size of the whole atlas. The engine would still have to load each atlas separately then, which adds to loading times. I would go with the third option.