Q: Best route down (east vs west coast)
A: By" down" I assume you mean south. Few have travelled both routes all the way. I know the western route in Central Africa and Southern Africa, although I haven't linked them, and know the eastern route from Kenya south, as well as Egypt. It's a question the answer to which depends on your interests and capabilities. People tend to consider the eastern route more interesting and easier, and I think that there are more "must sees" in Eastern Africa than in West and Central Africa, although it depends, as noted, on your interests.
Q: Timing (to avoid rainy seasons)
A: Look at
www.climatestotravel.com for everywhere on your route - it's not possible to generalise. When we last travelled long-distance in Africa we avoided the deserts in summer, the south coast in winter, and tried (mostly successfully) to avoid the various wet seasons. You need to build a base case for your estimated travel rate and then adjust for the seasons.
Q: Useful resources
A: T4A, iOverlander, maps.me,
www.4x4community.co.za; also look for blogs published by other travellers. Security questions are also addressed (albeit in a cautious form) by FCO.
Q: Visas
A: Depends on the passport(s) you hold - check for every country - the FCO Website is good for visa requirements, and if you search for "visa-free travel" on google you'll find a good reference in wikipedia.
Q: Camping rules
A: the answer is a wide range - Namibia, Botswana, RSA all have good campsites, Kenya and Tanzania also have good campsites although they are often more expensive. In Central Africa and North Africa you're on your own...
Q: "Must-sees"
A: depends on your interests - however the obvious list would probably include:
- the pyramids in Egypt, Maasai Mara or Serengeti in East Africa, Gorillas in Rwanda or Uganda (RSA is more of a security concern at present), Victoria Falls, Great Zimbabwe, Kruger NP, Okavango, Etosha, Sossusvlei, the Garden Route, the Congo River rapids...