If you wanted to drive to an absolute target you would need to keep track of your robot’s position using motion tracking. There are plenty of great resources for that on this website.
In order to have the best corrective abilities, you should use a PID loop (proportion, integral, and derivative). Using only the proportion to correct is known as proportion only control (P loop). This may work for a simple application such as driving straight but in general if you want to be as consistent as possible you should stick with a PID loop. The exact specifics are complicated but a PID is able to leverage the instantaneous change between adjaent loop which allows for another degree of correction.
Sample code for PID in vex: A PID controller in RobotC