My approach is to try and go modular. For example my sleeping bag is rated -3, but with a mid or heavy duty sea 2 summit thermal liner it stretches it into colder conditions. Or use a light weight puffer which you'd probably already have to boost what the bag can do.
Same for tent. Something that is easy to set up fly only or with inner.
Pack like the osprey aether 85 has a pretty capable day pack which attaches as the top lid.
For most things I'd stay clear of the cheap Ali express type things. NZ designed gear is designed for NZ conditions after all so I'd start there mostly.
Haven't watched yet but this might be of interest.
https://youtu.be/7oQqJ6565sA?si=wt6QfuNZM6POL7yZ
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