Hi, I'm a candidate from Nevada myself for the class of 2019. I also did the interviews this weekend too (I'm from southern NV, if it makes any difference).
They use the latter form you described from what I understand. There are no principle nominations in NV, nor is it possible to receive two nominations in our state. I've spoken to a congressional staffer, and pretty much what they like to do is convene with the other offices to give nominations. For example, both Senator Reid and Congressman Heck's panel may like a particular individual candidate, so what they'll do is decide between their offices who will nominate that person (I think they usually prefer their congressional representative to nominate them above anything else). That way, we have the best chance to potentially send as many people as possible from our state to attend a service academy, rather than put all our eggs in one basket by giving out two nominations to a person, who may potentially not even receive an appointment. Remember, the number of nominations available depends on the number of vacancies that a Congressman has at each academy for the particular year. For each vacancy a Congressman can nominate ten candidates to compete for the appointment. Theoretically, there could be up to 50 nominations if all slots were vacant for a service academy. But only 5 of those 50 would receive an appointment.
I was told again by this same Congressional staffer that you will hear something starting in January, so just be alert from the 1st all the way to the 31st.. Apparently they don't let us know any earlier as to avoid ruining our holidays if the chance we do not receive a nomination comes up haha.
If you have any other questions PM me, glad I'm not the only Nevadan on here!