One of us, one of us!
Uhhh, I'm not sure of the specifics regarding the nobles. My limited understanding is that the ranking goes, from lowest to highest:
Regular nobles
Those associated with the four houses
And then some government officials, probably, although there's a lot of overlap between this and the four houses.
As for new game plus though, basically everything is *available* to carry over, but for your first new game plus, you'll only be able to choose some things. You get five points, and you can choose between weapons, items, levels, your journal stuff, or even outright new things like unlimited bonding points, and bonus costumes.
if you were to beat new game plus, you'd get 10 points, and if you beat *that* new game plus, you'd get enough points to get everything.