The best you can do for good yaw reaction/stability is to level the motors (the error should be smaller than 0,5°). If you want to turn your motors a few degrees, that does not help in stability/reaction, it does help with "force", so if you have a big and heavy rig (with big and heavy payload) you get more turning speed on yaw, more force. But the reaction/stability is more controlled by the speed of your FC/ECS/Motor chain. The momentum on the motors does chance in the moment the ESCs raises power on the motor, the thrust of the motor comes along as the rpm changes which takes more time. So, from my point of view, take your time and level your motors on the X8, if you are not satisfied with the yaw behavior, level them better (and adjust the gains).
If you do "thrust-vectoring" on an X8 (coax setup), you have to take care, that if the top motor is turned in the one direction, the bottom motor has to be turned to the other, to support yaw.
best regards
Ferdinand