Natal can work (although a bit awkward) , so can Tormentas
portugese southern africa would be interesting in how it dfifered to boer and english southern africa due to their likely willingness to integrate mixed race subjects into the ruling class, likeyl giving them voting rights and integrating them into the white portugese populace.
The unwillingness to put mixed race people in the ruling class is almost entirely an American and South African thing, spanish, french accepted mestizos/gens libre de couleurs, brits accepted mixed race childs and wealthy creole in the carribean... this stereotype mostly comes from Brazil (for obvious reasons) and the fact that Portugal lacked so much manpower in African and Asia (both because of the coutry’s small scale and the high death rate from illness) that they naturally couldn’t afford to discriminate, in some places in Asia they even only cared if someone was Christian and understood Portuguese (at some point timor had virtually no Portuguese on it except some jesuits and the entire “administration” were converted locals who could speak Portuguese) They accepted Mixed race in Angola/Mozambique before the 20th century because they mattered, when they started sending hundreds of thousands of Portuguese post ww2 the mixed minority suddenly was often excluded from important job and the administration (and nearly 15% of the mixed races of Angola weren’t even considered “assimilados”, aka had the same right as White Portuguese)
Anyway quite a bit has been said about a Portuguese Southern Africa, I just want to say that where they colony is started matters a lot, make it in irl natal or Lourenço Marques and while it may be regionally important it will still be a disease ridden backwater (maybe not to the extent of say Luanda, but it won’t be a thriving settler colony), Portugal after all sent over a hundred thousand (at least!) people to Angola in the 4 centuries before 1900, yet most died or left.
If they start it in the more attractive cape, the settlers will adapt more quickly, and the Khoisan will sadly be assimilated as IRL into a mixed race population, although if there is a much larger Portuguese population than irl Dutch were, the coloured (current SA term) populaiton will likely become a minority among the white population of the cape , the opposite of irl where they are nearly 3 times more than whites in the western cape - a likely scenario since the Dutch were particularly poor settlers and Portuguese managed to send much more people oversea, and make them stick there (Portugal being a poor country certainly helped).
The downside of the cape is that it will take longer until someone discovers the rand’s immense ressources, which will be a truly transformative period for Southern Africa, even more than the discovery of the Gold in the minas Gerais was for Brazil. This - if Portugal still controls South Africa by this point - will likely change the colony from a strategic but secondary one to one that can rival or even exceed Brazil (if Portugal still has it/ever had it). Irl it took more than 200 years for the Afrikaner to discover it, and that was with the great Trek, although the larger population could speed things up.. It will be significantly quicker if they start exploring from irl Maputo.