If you're talking about what I think you are, it feels as though the trackpad resolution is way too low for precise aiming causing a juddering, jumpy cursor when trying to be slow and precise, correct?
I had the same issue trying to play Portal 2 earlier.
Make sure you're using smoothing in the mouse mode settings if the input is too juddery for you. Don't set it too high though, as it increases latency.
Mostly, I just use the trackpad for camera orientation. Fine aiming is performed using the gyro.
The problem is that you have a small surface. If you want it smooth and accurate, the sensitivity is probably going to be too low to orientate your player swiftly. Cranking the sensitivity up will ruin fine aiming and make things jittery. There are some options:
- Try trackball mode. This mitigates the small size of the trackpad somewhat, meaning you can use a lower sensitivity than with pure mouse mode. Make sure to play with the rotation setting to get a 180 degree swipe that works best with how you hold the pad and swipe your thumb.
- Use gyro for fine aiming and medium trackpad sensitivity in mouse mode for quick orientation of the character. I usually enable low acceleration on the trackpad and none on the gyro. Set the gyro to a low sensitivity.
- Try out mouse dampening. This reduces the trackpad sensitivity when preferred (perhaps when aiming down sights). Bind to your aim key, for example.
- Definitely remember to reduce the vertical axis sensitivity in mouse mode. I usually set it to half the horizontal. This really makes a large difference and helps you more easily get a rough bead on your target using the pad.