Yikes! As someone who really (thinks) they want to go Subs, would attending USNA vs NROTC change the statistics for sub commissioning? If not, how would one increase their odds while participating in NROTC, other than the obvious reapplication to USNA?
Well, there are a certain number of billets reserved for USNA and ROTC. It is not like they allocate more billets to ROTC if they don't fill enough of them from USNA. I'm not in NROTC, so I don't know specifics, but if you want subs I would choose a technical major, and take and do very well in your chemistry, physics, and thermodynamics.
Noticing your profile name, the fact that you are a female will make it significantly more difficult to choose submarines. There have only recently been female officers on subs, and right now I believe only SSBNs have females. It's an issue with berthing/bathroom facilities. They are going to expand this to fast attacks soon, but the Navy is moving very slowly on this. As consequence, there are very few female submarine officer billets, which means that the competition for them is extremely stiff. For USNA, I believe there are around 12 female submarine spots every year, and usually the girls that get them all have 3.8-4.0 GPAs. I really wish the Navy would move faster on integrating women into submarines, because it would help alleviate some of their manning issues in regards to the officer corps. Personally I think its silly to turn away qualified and motivated female applicants and then draft men that have zero desire or motivation to be in the community.
I don't want to discourage you, but I think its important to tell you how competitive it is for women upfront, so you can keep this in mind when you go through college. Hopefully in 4-5 years when you get ready to join the fleet there will be more female submarine billets.