I'm replacing some of my light switches with smart switches which support 50Hz 230V. They are meant to connect to the wires with twist nuts which are quite common in the US but not in NZ. I've read through the full domestic electrical standards guide for NZ and didn't see anything about if these can be used in NZ. My other question is about flush boxes. Are they required? Most of the ones you buy here are just for mounting the switch and not actually enclosed. In the US all connections must be made within a flush box but most things here just leaving the wires loose in the wall cavity. This doesn't seem safe to me. I just want to make sure I'm up to code and not causing any potential insurance issues. Also do I need to get my work inspected by an electrician if I'm just swapping switches? The code seems to only require this with new wiring.

Thanks