You need to really think about 3. Asking someone to sign in using facebook or twitter is much more than the physical action of tapping twice. you're asking for something emotional, their personal data. It would help others and myself if you posted what your app does. i would only use those as a form of login signup if your app absolutely depends on it - Tinder is a great example of this.
I completely agree. Using option 3 has its own set of con's, and this is one of them. Many Users have been misused/tricked in the past and don't like the idea of associating a new (aka unknown) App with their Social Media Accounts. For all they know the App will steal their data and spam their friends. This is in line with some of the feedback I get when validating with potential customers.
You may have hit a sweet spot there with option 2. Keep us updated! An interesting Metric would be comparing the Bounce Rate between these options above (ala A/B Testing).
