You should only adjust the global offset if you have audio issues.
Instead, you should adjust the hitposition of the skin you use. If you notice that you hit too early, lower your hitposition value. Otherwise, get your hitposition value higher but do notice the maximum hitpos value is 485.
You can check this out by playing an easy map and checking your hit error bar. If the line goes too much to the left, that means it's early. If it goes right, it means it's late. I suggest not moving the hitposition a lot just because you notice that you hit too early or too late on the harder maps. Stick to the number and start practicing your accuracy.