It is, probably, beyond the scope of this topic, but just adding or subtracting joystick axis’ values and passing the sum as the motor control value is less than optimal.
It will kind of work, but if user pushes both sticks to the max - the value will end up 100+100 => 200 and any value over 100 pct will be clipped to 100 percent motor power, which will make controls more sensitive over the narrower range of joystick positions when inputs are combined.
The drivers will eventually learn how to control it, but there are alternative ways to map dual inputs that preserve full usable control range:
Also, some people feel like exponential joystick mapping gives them better control and precision over the robot movements both at low and high speeds: