Whats is the angle precision of a 3 phases bldc motor?
The motor itself has virtually infinite resolution (minimum angle that it can be moved). Practical resolution is limited by the controller, which has a limited number of PWM steps. 

Having more poles is better because the controller's resolution is relative to each pole. The minimum number of poles is two, which produces a full revolution from 1 cycle of 3 phase drive. Your motor has 14 poles so it has 7 'electrical revolutions' per mechanical revolution, making its effective resolution 7 times higher.   

Precision is limited by random mechanical effects such as bearing friction and slop. Accuracy is affected by nonlinearities in the motor's electromechanical response. If run open-loop the rotor will not move by precisely equal amounts per step. So while you might get eg. 360 steps per revolution, they won't all be exactly 1&deg; apart. Torque ripple also occurs as the motor rotates, so any load will cause the rotor to be pulled off position by varying amounts.

Gimbal motors are normally run closed-loop with gyros and accelerometers providing feedback, which compensates for torque loading and nonlinearities in the motor.