Just got back from a trip to Taiwan and Japan.

I used Mighty Mobile (mighty ape mobile) for roaming in Taiwan and Japan at $8 per day with all plan features as if I was in NZ. I.e. unlimited data (50 mbps), calling and text to NZ and AU numbers.

When MM sends you a message to ask if you want to activate roaming, you must respond 'YES' to the confirmation message (no charge for that despite what your phone might say) then send yourself an SMS to activate the roaming.

• In Taiwan - no issues, just worked perfectly with automatic network selection.
• In Japan I had a problem with the default network it connected to automatically - Softbank. Nothing would work. I contacted MM support via app chat when on the hotel wifi network and they checked things promptly at their end. No issues found, the techie in me tried troubleshooting and to resolve the problem, I had to switch manually to NTT DoCoMo mobile network for roaming and then everything worked perfectly - this was in the first 4 hours after landing.
• I shared the roaming with my wife who was constantly connected to my phone via Wifi Hotspot (included in my NZ plan) so if you really break it down, it comes to $4 per day (24 hours, not calendar) per person which is cheaper than coffee for roaming.

I can recommend Mighty Mobile for roaming. $8 to use your unlimited data plan is cheap compared to eSIM plans available on the web which cost USD 5 - 10 as starter plans with not much data.

On OnePlus 7T Pro - Running Android 12.