I think in that video they are using sequencer or matinee to handle the camera movement
oneroncer’s method above would definitely work, and you could also change the scaling value in project settings.
Go to Edit>Project Settings>Input, In the axis values you should see Turn and Look Up, you will see that they have axis values of 1 and -1, change these to say 0.5 and -0.5
(For extra information, in the FPS character blueprint, this is the axis value in the ‘Input Axis LookUp’ and ‘Input Axis Turn’ Events. This might help you to understand how the system works better)