I've travelled this route almost every other month for several years now.
IME it's really a lucky dip as to what config you end up on. These sectors usually show the old first config operating far out and will then be confirmed around T-72hrs, although note I have had late changes (as many as two within T-12hrs) between all three possibilities. It really pays to keep checking closer to departure.
I generally stick in Zone A for the Old First version, upstairs exit row for the other two, although in the event of a last minute change it can be hard to secure decent seats upstairs, Zone A is a pretty good alternative which allows for a speedy exit at the JNB end.
As for which side, on the 63, A side is best for obvious ice views - although note in all the times I've flown this route I've only seen ice twice (both was in the winter months btw). 64 being overnight is pretty dark until about 2hrs before arrival.
Not a great deal of certainty for you I know, but there seems to be rather little on this route. I used to travel it in F until it was axed but was rather excited at the prospect of having the MkII skybeds. Alas perhaps due to the low competition, JNB seems to get whatever's available.
Cheers :-|