There are three types of scholarships awarded to finalists:
1. Scholarships awarded by colleges/universities. Some give automatic acceptance and scholarships to all finalists, but most award scholarships of varying amounts to those students who are accepted--which is not all applicants. To my knowledge, those kinds of scholarships are based solely on being a finalist--your actual score does not matter, nor does your ec record, etc.
2. Scholarships awarded by corporations. Usually, but not always, these are awarded by application to finalists who are dependents of employees. I don't know much about this group.
3. Scholarships awarded directly by the NM Corporation. A one-time $2500 scholarship. I think one's overall high school record is a large factor in this group.
Some colleges and universities do not award any national merit stipends, so if you do not get one of the direct awards, you may not reap any direct benefits. Many do give awards, though, and some are very lucrative. You will have to investigate each school to find out whether and how much.