September is supposed to be the best time to go to the Western Cape if you want to see wildflowers. However, if going to the Drakensberg January is a good time (although we haven’t done a tour there).
I agree, the Western Cape in September is amazing. We went on a privately arranged wildflower tour, travelling in two minibuses and starting in Cape Town; we also stayed at Simonstown (for the penguins), Langebaan, Clanwilliam and Montagu with visits to other towns and many nature reserves (for the flowers) although we also saw quite a lot of birds and animals, including Southern Right Whales at Hermanus.
Have only been to the Johannesburg and Pretoria areas and this was whilst working but would like to return and spend more time exploring.
We went in February but would love to go again, perhaps at the time of year you suggest.
One of the most beautiful areas is the western cape. In September the flowers are blooming,there are penguins and a lovely coastline to enjoy. Travel into the West coast national park where you might see Eland, caracal and red Hartebeest.
Small villages where there are individual gift shops and good cafes.