Do you understand how Airpoints works? Your questions don't seem to indicate you do because the concept of earning "miles" isn't really how it works in NZ.

On any Air NZ flight or Airpoints branded credit card you earn status points and Airpoints $ (APD). Status points go towards tier status with Air NZ, APD count towards flights with $1 APD equal to $1 NZD as you simply buy reward flights at the normal retail price. Unless you're spending serious coin you're not going to be able to buy many flights.

Most Platinum cards all have their yearly fees waived at present for new customers. I've been an ANZ customer for many years and told them last month I didn't want to pay my yearly fee when it was charged and had it credited back, however I would say this is an exception, not the norm.