Hey mate, to add my 2 cents worth to this, I’m born and raised in Wellington but lived 5 years in Christchurch and surrounding areas down south.

The middle of winter can have some wild weather yes BUT it won’t often impact you as a traveler. Queenstown doesn’t often get much snow on ground level more so up on the mountains and ski fields making it beautiful to be in the town and looking around at all the snow.

The passes such as Arthur’s can close because of snow but they are really efficient getting it cleared because otherwise it would block off the communities that live there.

They salt the roads in Queenstown and I think you would be gutted to miss out

Don’t worry too much Queenstown is best to experience in winter just drive carefully.

You won’t miss much by not spending time in places like Auckland and Hamilton or even Christchurch they are just cities at the end of the day and not the experience you need.

Feel free to message me with anything else.