I admit, it has always been a bit baffling that the Vampire Courts are grouped together when they are so distinct, so I see real value in trying to figure out their commonality.
However, the Whites to me are too weak to be a serious attempt by a major power-broker; they work because they are basically human (and so a real fight between them and a supernatural power almost surely drags in all humanity), not because they have so much power.
I rather think it's politics; the Red and White Court are politically aligned, so it suits them to call eachother cousins to emphasize the connection (even as they aren't nearly as friendly as they officially are). They also prey on humans, sure, but who doesn't? The Winter Court seems much closer to the White Court in their relation with humanity (i.e. a partly hostile parasitic presence that cannot procreate except with humans).
An alternative explanation is that it's their enemies who named them thus. We know the Reds are from the New World, where the White is from the Old. Perhaps the first Wizards to follow Cortes thought 'wow these yokels are oppressing the locals almost like our vampires' and nicknamed them vampires too, and then had to distinguish (the White Court being the Vampires of White people, the Red court of Red people). Of course this relies on the supernatural scene being almost as local as the normal, even though they have means of crossing borders more easily (as evidenced by the three Swords of the Cross having two European and one Japanese name).
As to why Ferrovax was at the party for Bianca - I think everyone but Harry and Susan knew events at that party were MUCH bigger than a simple noble being promoted. Bianca's promotion was an assault by the Red Court upon the spheres of influence of the White Council & Court, and attracted the attention of Winter, a Knight of the Cross, and a Dragon. Ferrovax may be the strongest individual present (and even that is dubious compared to the arbitrary power scale of the Knights), but the other Powers present together represent all the big honchos except Summer.
So, Ferrovax was present to witness the start of a War that led to the wiping out of one of the top Supernatural powers; not because it was an important noble, but because it was an important event.