I did this ride while circumnavigating South Africa. Hardly any traffic, the Anenous pass makes things interesting, while the wide open sections are ideal for checking top speed. I saw 263 km/h on my Garmin. Some restaurants in Port Nolloth. Take a jersey, the temperature drops quite drastically as one approaches the ocean.
Start point is Haenertsburg - use the Glenshiel hotel, it is stunning and clean. You ride past Ebenezer dam on the way to Tzaneen through sub-tropical orchards of fruit and avocado pears, as well as brilliant mountain scenery. Drop in at the Coach House Inn for the best hand made nougat in Africa (just South of Tzaneen). Albert Erasmus pass on the way to Orighstad is best taken at leisure. Robbers Pass gets really tight towards Graskop, but enjoy Kowyns pass going down to Hazeyview. Through WHite River and Nelspruit, you the New Pass on the road to Barberton which you definitely must take at the highest speed you can manage.