Campagnolo Front derailleur compatibility?

So I was just given basically an entire 2011 Campy Chorus 11speed group set for free, from a really good friend excluding the front derailleur and chain. I have never bought individual parts before so purchasing a front derailleur is foreign territory to me. I have been looking and I see you can get a braze-on, or ones with a a 32mm or 35mm clamp. No clue what this all means so could someone help me out. I will be putting the groupset on my 2011 full carbon cannondale synapse or my scott CR1, what front derailleur will work best with me set up and bike. Not sure if it's relevant but my cassette is 12-27. Thanks in advance for any advice!