Difference between Senegal and the other two W. African teams is tactical discipline. Senegal are vey well coached and have the luxury of having two leaders in defense in Koulibaly and Mendy. They are very experienced as well. To make it out of this group even without their best player is not an easy feat. Credit should go to their coach.
Ghana is also good, but not as tactically disciplined. But they do have a lot of energy which can make up for that. Cameroon has the least discipline, but are physically strong. It will be tough to qualify even if Brazil doesn't field their strongest team.