1. FWIW 2A or 3A are better seats. I know the story about the shape of the cabin giving a better view from 1A but having tried it I think it's inferior to either 2A or 3A where there's more space and a view which is just as good. You'll get sick of looking at the bulkhead if you're in 1A. Usually 2A and 3A are booked long before 1A so obviously the "regulars" prefer them. I guess you know that the LHS seats are better for seeing icebergs.
2. If hiring a vehicle I would suggest an SUV or 4WD. Sedans are fine on the highways but if you go into a place like Kruger (Sabi Sands is better) you will appreciate the higher ground clearance.
3. If you decide to drive between JNB and Kruger it's an easy self-drive but it's a bit boring to take the hwy both ways. Maybe consider a detour to see the Panorama Route which is west of Kruger - go to Blyde Canyon, God's Window, the Three Rondawels, Bourke's Luck Potholes etc. It's worth a stay overnight in a place like Graskop to give yourself enough time to do this as the scenery is unique. You could then enter Kruger from the west (I think it's via the Gowrie Gate) rather than entering from the south
4. As others have said, don't even think about driving through Zimbabwe to Vic Falls. Just fly into LIV or VFA to get the most out of your time. Vic falls isn't very big so you will find the bridge and falls are within easy walking distance.