Non conformity is not something you choose as a tool (if you're a thinking adult of course). It's a consequence of your beliefs and reasoning, which you will not give up no matter the benefits.
Everyone is likely to have a mix of niche and mainstream interests, when they stop concerning themselves with fitting into a narrow vision of who they are.
Can you still be a non-conformist if you have similar interests to the mainstream?
You can be a non-conformist and have mainstream interests, but just as a conformist will neglect non-mainstream interests for the sake of conformity, a non-conformist will do the reverse.
Now people will get labeled by others as conformist or non-conformist based on outward signs, and this will often be overly inclusive since someone who is neutral to conformity cannot, in some cases, easily be distinguished outwardly from a conformist, if their interests are mainstream, or a non-conformist, if they are not.
To me, most labels we attach to ourselves requires a certain level of maintenance. If I call myself a geek I have attached that label to certain interests I have, if those interests change does the label lose its meaning?
What I'm really saying is that a self-identified non-conformist has influenced their tastes in the future, whether they admit it or not. If that label is applied by others then it need not have the same effect.