You missed one – the third choice, which is neither a mitzvah nor an aveira. (This is known as the fallacy of the excluded middle).
For example, the choice between eating a tuna fish sandwich or a peanut butter and jelly sandwich. It’s my option which to choose and neither choice is a mitzvah nor an aveira.
The Wolf
Not according to the chovos halevovos (tuna fish is probably healthier, unless yo had a couple that week, but jelly is all sugar so I’d still probably go with the tuna)