It is a very good choice for this purpose.
Larger calibers with the same shot placement and the same bullet will perform better, however the 9.3 is more than capable in the right hands with the right bullet and shot placement.
No! 9.3 and 375 calibers are not recommended for frontal chest shots on buffalo.
Yes with the right solid and shot placement it has more than enough penetration to reach the brain every time.
I would not recommend the Barnes TSX in the 9.3x62 for DG.
It is a great Lion caliber but do not use lighter weight bullets, use minimum 286gr or rather step up to 300gr or even 320gr bullets. The Woodleighs in the heavier weights are excellent for Lion.
It sure is a legendary caliber and with the right bullet, shot placement and in the right hands it can kill anything in Africa.
In many cases the reduced recoil results in better shooting ability and shot placement which in turn means dead whatever you where aiming at.
It is a superb caliber, great for plains game with the ability to kill DG more effectively than what ballistics suggest. Anybody who has used one will only have good things to say.
Good luck and enjoy one of the best African calibers ever designed, the Germans knew what they where doing....