Freebird, your response came as we were traveling NZ and I concur with your findings. We did not get a WISE card. Our plan of attack was to use credit cards and to withdraw $200NZ from an ATM.
We ended up not even getting cash until about 7 days into the trip. We used credit cards for everything. We are not souvenir shoppers, so most of our expenses were gas, grocery, restaurants. Almost all our lodging was paid thru booking. There was not a surcharge for gas or groceries. It seemed about half the restaurants added the cc surcharge. The few times I purchased souvenirs/post cards, there wasn't a surcharge but I'd guess I was lucky. We always inserted our cc never used tap/paywave.
We paid a fee of about $5NZ, at the ATM. I'm told some ATMs do not have fees in NZ. However, we were in a VERY small town and the fish and chips place only took cash. We actually came home with about $60NZ because places in Auckland at the end of our trip wouldn't take cash! We will likely return so no big deal.
The only issue we ran into with money in NZ was it was difficult to reimburse a host for mailing me clothes I left behind. Venmo isn't used in NZ, I didn't have WISE and neither did the host, so that was a moot point. She suggested a bank to bank transfer which apparently is a "thing" in New Zealand. However, even if we wanted to share that info, we aren't set up to do that. For lack of any other idea, I mailed the cash. It was just $10NZ so it was worth the risk. She did receive it in a couple days. Incidentally, $10NZ to courier a package from one island to another. WOW! That amounts to about $6 U.S!
Also, regarding paying for gas-- When we would insert the card at the pump, it would want a PIN. None of our cards have PINs. So the first few times I went inside and the attendant, would tell us to go ahead and pump. Finally, an attendant told use to ignore the prepay and just pump and pay inside. That worked at every gas station. I think the issue came down to needing a signature for U.S. cards. Not sure why, but it all worked fine.