Furious Focus and the Overhand Chop abilities function differently in this context.
Applies to the first attack roll in a round, regardless of where it's coming from (notably, because it doesn't depend on there only being one attack). So the initial attack from Cleave and associated feats wouldn't take the Power Attack penalty with Furious Focus.
Only applies if you make exactly one attack with either the Attack action or a Charge, as specified in the text. Cleave and Great Cleave are not the Attack action, nor are they a charge, so they do not get to apply. However, you can use the Attack action to make an attack modified by Overhand Chop, and then get another attack from Cleaving Finish (though this extra attack doesn't get Overhand Chop's extra damage).