There is very limited knowledge I have but I believe there are one hundred spots for appointments under the presidential nomination. I personally recieved an SDVET nomination. I have no idea under which nomination i was appointed under (recieved 5), but all I know is that the more, the better.
There are an unlimited number of Presidential nominations allowed and everyone who is eligible gets one. However, there are only 100 appointments allowed to be given under this category. Most years the academies have roughly 500-800 nominations given to Presidential-eligible candidates. I do not think that Presidential nominees who are not given an appointment move on to the NWL.
Presidential: 100 appointments per class; unlimited nominations
Criteria - Children of members of armed forces who:
are on active duty (other than for training) and who have served continuously on active duty for at least eight years
are, or who died while they were, retired with pay or granted retired or retainer pay
would be, or who died while they would have been, entitled to retired pay except for not having attained 60 years of age
Caveat: Those eligible for selection under section covering children of KIA, Disability, etc. are not eligible for Presidential appointment
Example Class of 2016: 91 offers of appointment to Presidential nominees, 71 acceptances
It is my understanding that for USMA all 3Q + NOM candidates are placed on NWL - I believe this includes all nomination sources including Presidential, but not positive. However, if your DS gets a 3Q letter, it will say whether or not he is on the NWL.
The NWL would only come into play if there were more qualified candidates than Presidential appointments available. As seen in above example, there were enough appointments for all qualified candidates.