1. NRE's leave active duty after 5 years, but may be able to stay on as a civilian government employee at NR. If you want a "lifelong commitment" in uniform, Subs or SWO-N are the only nuclear options.
2. Some (very few) NROTC mids are accepted as NRE. Your grades in college will determine if NR will consider you for this. The majority of nuclear mids are assigned Subs.
3. I'm not too familiar with the Reserves, but I'm not sure if there is any benefit to doing it if you are just planning on applying for an officer program a year later. I don't think you'd get much worthwhile experience in a single year in the reserves unless you are deployed or are activated, which you are trying not to do. It may be more worthwhile to use that time instead to focus on your schoolwork to keep your grades up to improve your NROTC/NUPOC application. If its a money issue, maybe you could get a student job at your school working for a professor to do something more relevant to your major. Just don't be one of those guys who had great grades in high school and then go and tank your first semester of college because its a new and unfamiliar environment, cause that will hurt your chances for both programs.
4. You could also see if they'll let you take the NROTC course as a non-scholarship freshman to get some Navy exposure. You say that are not too familiar with the job of a SWO, this would give you some interaction with actual Navy officers who can tell you about the job. Subs/SWO-N are the more mainstream Naval officers leading sailors operating the nuclear reactors onboard ships that go to sea to accomplish whatever mission they are given. NR Engineers have a desk job in DC and interface with the laboratories, contractors, and other government entities to provide the oversight of the entire program. Two very different jobs.
5. If you go NROTC, you have a decent chance of getting interviewed for nuclear if your grades are good, however realize that there is a much greater demand for Sub officers rather than SWO-N so you may be assigned that. Also, if you aren't selected for nuclear you'll be committed to another field in the Navy, so you need to be prepared for that. If you aren't willing to accept that, it may be better to wait and apply for NUPOC.