score:11
Kiwi here, I've moved to Australia. I fly back and forth reasonably regularly with prescription medication (heart, anxiety, other).
I don't take a letter for the meds, as long as they're in their prescription bottles (with your name) they're fine. Always declare them.
Upside: The 'declare' customs line is often shorter, and they almost always just wave you through.
Downside: Very occasionally you get taken aside for questioning (are the drugs for you? Do you have enough for your stay?), but that's the extent of it.
I've asked a couple of times and the customs officers have always said to declare the medication, both in Australian airports and New Zealand ones.