Hi, I think Ryan’s reply essentially said everything you need to know.
Even though it is called Nothing OS, it is still fully based on Android, which itself is rather secure as long as you, as the user, act with common sense. Don’t sideload apps from sources which aren’t trustworthy, stay away from shady apps and websites and so on.
Nothing provides roughly bi-monthly security updates and for Phone (2a) I think they state it’ll get three major updates, so Android 17 would be the last major version for that phone. Security updates are stated for four years.
While I’ve never owned an iPhone, I know they are well known for their great camera performance. While the Nothing Phone (2) offers solid cameras, I think they won’t be able to compete with an iPhone (or more expensive Android phones). For instance I am using a Galaxy Fold 4 as my secondary device, which for Samsung terms comes with a decent, but certainly not Ultra flagship level cameras and overall it performs better in pretty much all camera-related aspects compared to my Bothing Phone (2).
If you like to just dip your toes into the Android world with Nothing, I suggest looking for a Phone (2a): It offers a great overall package at an affordable price, you get that signature Nothing design, the Glyph interface (although more basic in terms of looks), good battery life, performance and display. From what I’ve seen, even the cameras seem to be almost as good as those you’d find on the more expensive Phone (2).
Hope that helps!