A hire car is almost essential for exploring KwaZulu-Natal beyond Durban. The distances are real — from Durban to the Drakensberg is three hours, to Hluhluwe-iMfolozi another two and a half — and public transport doesn't reach the places most visitors want to go.
The N3 and N2 are excellent toll roads. Secondary roads are generally good, but off the main routes quality drops quickly. A standard saloon car handles most of the province; a 4x4 is only necessary for specific tracks in game reserves or mountain areas.
Within Durban the options are taxis (metered and reliable in most tourist areas), the IRTT rapid bus transit between main points, and Uber — which works well in the city. The downtown area is best navigated with local knowledge or a taxi.
For game reserves and wilderness areas, guided tours make sense for first-time visitors. Most lodges arrange transfers and game drives. Self-driving in parks like Hluhluwe-iMfolozi is possible and good; you'll cover more ground on your own time but miss the commentary.
For the Drakensberg, the main resort areas are reached by good tar road; the trails themselves are on foot.