You could honestly spend a month in any of those countries, and barely scratch the surface of all the cultures, people, and ecosystems. I would highly recommend Ghana as a base, due to its stability, infrastructure, and low corruption. If you send me an email (link in profile), I'd be happy to connect you with interesting people in most of the countries you listed as well as Kenya.
I spent a year in Ghana in 2017, and I had the pleasure of meeting numerous software engineers and tech entrepreneurs who were doing extremely high quality work for 1-2k USD / month (if they were lucky). Having companies like twitter on the African continent will provide massive economic opportunity, and social mobility.