Accela in opentrack 2.3 no longer contains many overly complicated settings.
There are two smoothing sliders, for rotation and position each. They're expressed in different units.
Smoothing makes small movements take effect slower. This is useful to prevent natural head shaking resulting in the view swimming all over the virtual cockpit. As well as natural tracker inaccuracy causing jumping around each frame, since very slightly different pose is returned each time.
Deadzone ignores minor movement completely. It can be useful for extremely noisy input. Try not to use it excessively to avoid losing precision. For camera-based trackers, rotation deadzone of 0.1 degrees is already pretty high.