Here are two general advices that can help you to keep your soundtrack as reactive as possible.
1. Always keep the Pre-Beat times short
When the playback of a Segment is approaching its end, psai will start to evaluate the next best-matching Segment. A short interval between that evaluation and its playback means that psai adapts quickly to recent changes of gameplay. The point of time when the evaluation starts is directly affected by the longest Pre-Beat time among all Segments that could possibly be enqueued next. E.g. if there is a compatible Segment with a Pre-Beat time of 5 seconds, psai will start the evaluation at least 5 seconds before the current Segment is over. This way it is made sure that there will be enough time to fully play that Segment from the beginning, in case it's chosen for playback.
So to to make sure a Theme is as responsive as possible, use the Pre-Beat periods only for short fade-ins, and try to stay below one or two seconds. Bear in mind that a single compatible Segment with a long Pre-Beat period is enough to potentially screw the responsiveness of a whole Theme.
2. Keep your Main Regions short to make your soundtrack react faster
The shorter the Main Regions of your Segments are, the faster psai can react to sudden changes of intensity. Therefore to fully tap psai's potential, we recommend to limit the Segment duration to 4-5 seconds for Themes that demand a high level of adaptivity (like Action Themes). The Pos-tBeat regions can be as long as you wish, as they do not affect the timing of following Segments.