Central Otago rides are good place to start.
Classic Otago rail trail, Lake Dunstan, Clutha gold trail. Weather is best between Oct-April, typically warm and sunny. Can still be good in May as this month is lot milder in last few years thanks to global warming. Expect some frosty starts in April and May.
Alps to Ocean is also awesome ride.
For all these rides work on 40-60km day on ebike as you want plenty of time for stops and sight seeing.
I've yet to do Waikatio river trail but heard its bit more technical in places.
Timber Trail can be awesome ride when sun is out which was case for 2hours on last day rest of time it was steady rain. Was glad we had MTBs with decent MTB tires.
West coast is great trail but bring good wet weather gear good chance you will need it.
Most people do these rides oneway and in process miss a lot. We've ridden a few sections out and back and discovered scenery can be quite different on return leg. Especially in mountains.
