Twist
On a practical level...no difference. It will change the direction that the bullet drifts, assuming zero wind...which is pretty rare. A RH twist will cause the bullet to drift slightly to the right. It doesn't amount to much. Maybe a quarter-inch or so per hundred yards, depending on the bullet shape, mass, velocity, etc...but a slight breeze in the opposite direction could easily counteract it.
It will cause the rifle to recoil differently, which may have more of an influence on the bullet strike than the drift. Since the gun is in recoil before the bullet leaves the barrel, whichever direction the rifle moves the shooter when it kicks will affect the bullet's path. Some people move more than others under a rifle's recoil...so this won't be a constant that you can calculate. It's also why each shooter should zero his own rifle. Only rarely
will a rifle zero the sasme for two different people.
With pistols, it can make a more noticeable difference. The 1911 pistol has a LH twist. This causes the gun to torque into the palm of the right hand under recoil..keeping it more stable. If you fire the gun in the left hand, it will torque away from the palm, which is less stable...and the gun will arc and
turn almost horizontal unless you have a very firm grip on it. Using two hands negates the tendency a lot.