Conform is NOT what you want. That is used to create slow motion effects.
Sounds like you just need basic multicam training. First, I'd Optimize everything into ProRes 422 when I import it all, to make the multicam run more smoothly.
I'd highly recommend Ripple Training's multicam tutorial series, which is a fantastic deal for $30.
http://www.rippletraining.com/categories/final-cut-studio-courses/final-cut-pro-products/multicam-editing-in-final-cut-pro-x.html
The user manual has extensive information on using multicam. You need to open the angle viewer, the angle editor, and have it in a project, all at once. The angle editor is where you're going to tweak your syncs. Also, place a marker in each of the two clips on a common location. FCPX will analyze the audio around the markers making audio sync faster and more reliable.
http://help.apple.com/finalcutpro/mac/10.0.4/#ver23c76439
Frame rates don't matter, but audio sample rates do VERY much. The video standard of 48kHz/16-bit AIFF, but the iPhone records at 44.1kHz. What I would do is create a droplette in Compressor for a ProRes 422 custom preset at 48kHz, and run the iPhone footage through that.
But I've never used iPhone footage in a multicam before. I'll have to test that out some day.