Thanks for using Syncfusion products
Query 1 : Currently, I have 4 series at 100k points each and the zoom and scrolling is very laggy.
We have analyzed your query, we have improved the trackball lagging issue by using BinarySearch in UWP CustomRenderer. Please find the sample from the following location.
Query 2 : The problem is that if I change the item source of my chart, I can't zoom further back. I want to be able to zoom in and out but don't show too many points on my chart.
We have checked this problem with our sample, this works fine with changing ItemsSource. So please check the sample from the following location. If still you face the problem, please revert us by modifying the sample based on your application along with replication procedure. This would be helpful for us to serve you.
Thanks,
Muneesh Kumar G