I have hunted Africa either 14 or 15 times. I've messed around with different bow and arrow weights.
This is opinion, so take it with a grain of salt...
Number one in importance is not bow weight, it is ARROW WEIGHT! Try to get at least 600 grains of total arrow weight.
Number two in importance is the broadhead. Use a STRONG, two blade head. I use the Magnus 135 grain on plains game and the Magnus 125 on heavy boned animals, such as Cape Buffalo.
The least important is bow weight. Accuracy is far more important. Having said that, however, anything much under 60 pounds is not going to drive a 600 grain arrow through one of these animals.
African animals are so much tougher than North American game that it defies the imagination. No one wants wounded game and light tackle and lousy broadheads just increase your odds of problems.
Just opinions, but based on a lot of African experience.
I shoot a 64 pound bow, either a Morrison, or a Wolverine. My arrows weigh 640 grains all up. I use the same bow for Buffalo, but with 960 grain Diamond Wood shafts and the 125 grain head, which is narrower than the 135 grain head and will get through bone better.
FORGET KINETIC ENERGY!!!! Use your head on equipment and remember that you are a traditional archer...that also means "Primitive". Primitive man didn't screw around with "Connecticut Energy"!
Too Short