By the mid-1980s the South Africans developed several (around six active at any one time) enriched-uranium gun-type weapons that could be delivered from several platforms. They had research programs into implosion and thermonuclear weapons but apparently made little progress. The whole project was very underfunded for a nuclear weapons program; on the order of $10 million in present USD per year until further development was cancelled in 1989. (By comparison, the US spend on average about $80 billion a year in present USD on its full nuclear program, including delivery vehicles, during the Cold War, and is set to spend some $20-50 billion per year maintaining and modernizing its capabilities for the next 30 years.)

So that is a very modest nuclear weapons capability, capable of being used locally but not globally, and a very small stockpile indeed. For a lot of details, see David Albright and Andrea Stricker, Revisiting South Africa's Nuclear Program (Institute for Science and International Security, 2016). It has the most technical and programmatic detail of anything I have seen.