If WW3 happens how messy wiil Africa be?

It will be a complex situation depending on who goes to war with whom.

The dominant political discourse in South Africa is generally "anti-Western", as a hiccup from the Cold War era liberation movements, who lean towards China.
Russia is a red herring these days. a business partner for some politicians, but they're increasingly seen as racist and anti-leftist.
On the other hand, we also have US military bases (notably at Waterkloof); SA helped with renditions during the US-led War on Terror (although we also have ISIS de facto training camps), and while technically illegal, white males with military training from the previous regime (which conscripted all white males) formed the third largest unofficial military force in Iraq and Afghanistan. The ANC didn't like that, but could do nothing to stop it, and aging white males had little option but to become mercenaries after President Mbeki kicked them out of the defence force.
Their service was much lauded, to the chagrin of Mbeki, whose socialist trained army had their weapons stolen from under their noses during interventions in the Congo.
Although arguably that white demographic is likely to be over forty now, and no longer the fittest.

Much of our historic leverage was taken by the dismantling of our atomic bombs (another sore point for the ANC - the world didn't trust them with nuclear weapons), and decreasing production in our once famed mines (with continuing labor issues).

Then politicians seem to be prostitutes to the highest bidder rather than having monolithic national interests.
Our neighbors are similarly divisive, with successful Botswana aligned to the US, and Zimbabwe (although an economic nightmare, their army nevertheless is now more effective than ours) having traditional ties to China and even North Korea.

My sense is that we will be a nation of mercenaries without a singular conscription or national interest.
We already employ mercenaries (largely from central Africa) as private security at institutions with major unrest, like university campuses. The loyalty of locals to the state can no longer be guaranteed. Most of the state apparatus will be needed to quell local unrest, but many will fight abroad as mercenaries for financial or ideological reasons (a bit reminiscent of World War II).

That will be the role of Africa.
In fact, not only Africa - it will cause unrest to the point of civil war if general conscription is enforced in even most Western countries.
World War III will be professionally privatized.
It will be run by companies alongside limited voluntary national forces.
You pay - we fight.

It's a complex situation.

In South Africa you could have three black ANC ministers sitting next to each other in Parliament (and the party has gone virtually all black).
They could belong to three different tribes - and tribalism still matters.
Gender still matters.

They could be tied to three different business interests.
One might be linked to India, another to China, and another to the USA.

In such a situation - who will fight for whom?
Only a really powerful leader could galvanize such patriotism, or we would have to be fighting what everyone sees as a global threat. Maybe an alien invasion.

Generally, not all of Africa is a basket case.
Many places are doing vibrantly well.
That should be highlighted more.
On the other hand, there should be less excuses for failed states - bad governance is bad governance.

a reply to: makemap
I am going to reply with the understanding that WW3 has been ongoing from 2009 when Russia offered its first kinetic resistance to NATO's influence creeping up from Georgia through South Ossetia and Abkhazia.

The current battleground already span a similar geographic distance on the same continents. People seriously need to rethink how they are analyzing a global conflict nearly 72 years after the end of the last one. The world's technology, cultures, economies, and especially battle doctrines have evolved significantly since to the point, they are really no longer the same world as far as warfare is conducted, although the objectives remain similar.

USAFRICOM regularly conducts joint training with Africa's largest and stable powers within the framework of mutual interests. France, UK, and Italy fill in many of the gaps as well. Western multinationals maintain quite the political and economic clout in these same states. Let there be no doubt, Africa is in majority aligned with the interests of the primary NATO member states. There are holes here and there, but they would be no significant threat in an expanded campaign if we preferred to roll back to antiquated battle modeling which does not really apply in today's world.

I have to laugh at the idea anybody honestly believes China and India have any kind of animosity that would warrant one to fight the other. India is only thirsty for Pakistan, and if got hungry too, maybe Nepal and Bangladesh. China and India still have very well preserved ancient cultures running their societies. They just are not knuckle headed enough to get that angry at each other for a reason to put nearly half the worlds population at war against each other. It is illogical. I don't even see it making sense in a video game, but a B movie maybe.

I do like to draw parallels to WW2 though as far as objectives and locations though. WW3's current Africa hotspot spans from Central North/Med. to the Horn of Africa. Then from the Arabian Peninsula upwards into Syriac. See its very closely similar distance and size as WW2, it all just kind of shifted Eastward a bit away from Europe, although they are still feeling its consequences.

Pacific campaign could either be super hectic, and is likely where we will once again see the deployment of WMD', but likely nearer he end, identical to WW2. Or it could just fizzle out.

Philippines is expanding military capabilities now on a disputed island with China. I'll let you guess who is backing that, it would be the same people they regularly train together with.