Hi Sean,
Thanks for contacting Syncfusion Support.
Query 1: Regarding formatting the trackball
We can achieve this requirement (customizing the FontSize) by using the TrackBallLabelTemplate property of chart series and we can round off the label value into 2 decimal digits by binding the label value using converter
Query 2: Regarding controlling the “mouse over” programmatically
You can programmatically control the trackball by using CustomTrackBallBehavior. We can We have prepared a demo sample based on your requirement and it can be downloaded from below link,
Regards,
Devi