Hi Eli
There are a huge number of wineries in the regons you mention, most very close to each other and certainly more than you can possibly visit.
First things first: you *must* get as soon as you arrive 'Platter's South African Wine Guide'. This annual (since 1980) guide reviews and rates wines, giving detailed winery info, visitor info, maps etc. New edition comes out at end of year, or you can get it as an app -- see
https://www.wineonaplatter.com/platters_appQuestions:
1) When will you be there and for how long?
2) Are you renting a car?
3) If not, how will you visit wineries?
4) How many bottles do you intend bringing back with you?
5)Have you though about buying them there and getting them shipped home to you - depends on your home states laws
All types of wines are made. I think you are wise to focus on Pinotage & Chenin as they are RSA's iconic varieties.
Regarding picking up wine to drink when you are there, note that most restaurants allow you to bring in your own wines at zero or minimal corkage without batting an eyebrow.
Avoiding high alcohol wines will be difficult; the winelands are quite hot and wines tend to have around 14% abv.
The top name in Pinotage is Kanonkop Estate, just north of Stellenbosch on the R44.
Their estate Pinotage is made from some of the oldest Pinotage vines in existence, if you visit the classy winery they also have open for tasting and purchase a 10 year old bottle; when I was there earlier this year they had the 2007 vintage as well as the latest release.
They also do a barrel selection of the estate wine, with a black label, rare and expensive
(Prices at winery Estate 2015 Pinotage 350R (26 USD) Estate 2015 Black Label 1595R (120USD)
They are also known for their Bordeaux blend
see
http://www.kanonkop.co.za/Best know of the Chenin producers is Ken Forrester, his flagship Chenin is 'The FMC'
http://www.kenforresterwines.co.za/But there are many fine producers of Pinotage and Chenin, much made in small quantities by people who don't have wineries open to the public, but whose wines might be found in one of the specialist shops.
In the winelands, Vineyard Connection is close to Kanonkop and they also ship wines abroad.
https://www.facebook.com/TheVineyardConnection/Look for Beeslaar Pinotage there.
This is a singe vineyard Pinotage made by Abrie Beeslaar, who is Kanonkop's winemaker. The 2015 has got 98 points and been chosen by Tim Atkins MW as his red wine of the year in his annual South African Wine Report.
http://www.beeslaar.co.za/But so many wines- Platter rates 8000 wines fom 900 producers in the 2017 guide.....