With a wheel that turns farther you are going to have to turn the wheel farther to get the same throw. It takes time to transition the wheel back and forth. Think like in a 1:1 f1 car. they have really fast racks. With a slower rack you would be more precise, but not as quick as it takes a long time to transition the wheel.

If you want to be more precise through the travel of the wheel lower the dual rate. This lowers your max throw, but raises your input output ratio of the wheel to the wheels of the car. So for example it may be 1:1 but with reduced dual rate it may be 1: .75. This is usually fine as you never use full throw in most situations. Most high end radios have options to lower your throw anyways.

Messing around with expo is ok, but also has reprocussions at high levels of steering throw making the car react much faster than at lower throw. Adding expo should be a action done sparingly.