Lovely to hear from you. Year 10 was around when I started really strategically focusing in US admissions. To get into a top university in the US like Harvard, your performance is assessed from Year 10 to Year 13.
Firstly, I would ask you to re-consider the strength of your focus on NCEA and IB. With CIE, you can re-sit exams regularly and there are sittings in both May/June and October/November. IB is actually more scary because your main exams are all at one time after 2 years whereas for Cambridge you have many smaller exams spread over several years (at IGCSE, AS and A2 level).
NCEA is the weakest option and prepares you the least for success within New Zealand or overseas. Medical school students at University of Auckland often cite how much NCEA Chemistry students struggle with the first year of university. In contrast, IB and CIE students thrive and find the content very easy.
You can stand out in NCEA by taking many subjects, getting Dux, winning subject awards, winning academic competitions, taking NZQA scholarship exams, taking AP exams, taking SAT Subject Test exams or taking CIE on-top of your NCEA as my student Soumil Singh did with our guidance: https://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11620752
There is substantial strategic complexity on what to focus on and it depends on your skills, interests and ambitions. The optimal strategy varies considerably and I would need more info to advise more specifically.
For IB, yes - taking 4 HL subjects is better than taking 3 HL subjects. Within each subject, there is variance in the rigor. For example HL Mathematics is viewed as being one of the most challenging and its very necessary for certain highly competitive STEM degrees.
The advantages of going overseas depends on the quality of university you attend and what you want to focus on. Assuming you have the ability and leverage the right strategy and training and can get into one of the standard schools Crimson sends New Zealand students into like Harvard, Yale, NYU, Duke, Cambridge, LSE etc which are much higher ranked than domestic universities like University of Auckland or University of Otago. If this is the case the benefits are: 1) smarter classmates driving more powerful networks 2) better and more acclaimed Professors 3) access to the world’s best jobs at companies like SpaceX, Tesla, Google etc which are almost impossible to get into from New Zealand universities 4) access to investors, labs and research to help propel your career forwards 5) stronger candidacy for graduate school if you want to go into PhD programs or other advanced degrees 6) higher salaries and earnings power 7) MORE FUN - many US schools have amazing on-campus cultures with 99% of undergraduates living on campus and this builds a far more engaging experience than New Zealand universities in which students mainly commute in. Virtually 100% of students who get into overseas universities from New Zealand from Crimson go overseas because the opportunities are so attractive.
Rangitoto has introduced IB but is relatively new and has some of the same challenges as Scots College where many of the best teachers don’t want to teach IB given their familiarity with IB. I would recommend going to St Cuthbert’s or Saint Kent’s College over Rangitoto. You can supplement your IB program with Crimson’s elite IB tutors to help learn the content faster and bridge the gaps at schools. Student experience of IB varies a lot based on the school and your own skills and learning style which you can tell me more about.
NZQA scholarships are well understood by overseas universities like Cambridge, Oxford, Harvard, Yale, Princeton and Stanford. Many Crimson students sit NZQA scholarships every year in New Zealand and dominate the exams. It is dangerous to do NCEA with no NZQA if applying overseas.
Please send me an email at firstname.lastname@example.org with your CV, current subjects and more detail on what you like within STEM and I can give some deeper insights.