You could maybe get up to 60% in South Africa but that would be a big stretch and require significantly more immigration than OTL. The only other spots would be Kenya and (ex)-Rhodesia for Britain and Southwest Africa for Germany, those could perhaps get up to South African levels of Europeans in them if the colonial powers really work at it.
Don't forget parts of Tanzania, Mozambique, Angola, and Katanga, which have similar climates to Rhodesia and would be suitable for Europeans. Angola and Mozambique indeed did have hundreds of thousands of Portuguese in them before their wars of independence.
One thing to keep in mind is that often Europeans didn't want a settler colony. British Kenya kept out poor whites because it was supposed to be a playground for the rich.
True, and I believe Rhodesia as well had immigration restrictions. Kenya easily could've gone the path Rhodesia did if it had only a few thousand more whites. And it would've ended in a very similar way. The only future for Europeans in Africa was basically to accept that times had changed and embrace minority rule on a fair basis. And hopefully you'd have governments which would tolerate no violence against either whites or blacks (or anyone else like the large Indian minority).
Yes, just so they can obtain a south Africa look
They could, but remember that Europeans "sterilised" themselves all the time too, through birth control methods. Vasectomies were originally associated with the eugenics movement (forcible vasectomies were employed), and were used to control birth rates in the third world as well.
Your OP post implies development of what we call the Third World, and birth control is only a part of that development. Historically, birth control promotion (be it sterilisation or otherwise) has been used as a sort of cure-all and overemphasised for the issues faced in those regions--it certainly helps, but is by no means the only thing needed.
Indonesia, by the way, was also a deathtrap for Europeans. Over a million Europeans died either in the Dutch East Indies or en route to the Dutch East Indies of disease. The population growth of Europeans in Batavia was effectively stagnant.
If you consider Latin America "white" (most of them are pretty much white plus American Indian genetically, and culturally more or less Western), I think you could do something similar to South Africa. But as I said, you're replacing the "Native American" component in Latin American ancestry with an African component, and you'll get something that looks like Brazil (very multiracial) rather than some "Europe in Africa". MAYBE on the coastal fringes like Mozambique and Angola you can also replicate that, but the interior lands of Africa (Katanga, etc.) which are good for Europeans are too deep into there to be colonised at an early enough date to Europeanise the locals.
North Africa can become European if you just change the definition of European. Genetically, the populations aren't too far different than Southern Europeans, and if there were no Islam, they would've developed a shared culture with Italians, Spaniards, and those on the other side of the Mediterranean. The Maghreb would've spoken Romance languages and maybe been particularly "European". Egypt and the Levant would've retained a less European quality, but still have been part of that culturally "European"/Western realm (Egypt would've spoken Coptic, the Levant would've spoken Aramaic). The populations of the Levant and Egypt are likely to look similar to today in any case, just culturally and linguistically different.
