The Radeon HD 8400's performance is between the Intel HD 3000 and Intel HD 4000 graphics core. But it is closer to the Intel HD 4000.
You should be fine playing graphically low demanding games at 1366x768 resolution using low or a mix of low and medium graphic settings. If you are hoping to play GTA 5 on it whenever it is released maybe you can get decent performance with everything set to low. But that depends on how well / poorly optimized the console port will be. You might get decent performance in BF4. Decent performance means around an average of 25FPS - 35FPS.