I can't help you with AF since I haven't flown them in ages but here's what I think for EK:
Although not class-leading, I think the 77W product is quite good in F on the EK 777ERs. It is fully flat.
I am not sure which flights you are looking at for connections, but you can a nice connection to JNB
EK 6 LHR 22:00 DXB 08:45 +1 EQV 0
EK 763 DXB 10:15 +1 JNB 16:25 +1 77W 0
However, I would only recommend this if you choose a day when EK6 is operated by a 777-200 or 777-300ER (both have identical F seats) and not if the flight is on a 777-300 (old seats, though there is a chance they will be new by December.)
On the way back, if you pick up the new 4 x weekly flight EK766 you can connect to EK029 (1h 20m connection in Dubai) but again, only do so if EK029is operated by a 77W or 772.
Cheers