@astounddotmedia @kebiro thanks for your feedback! Which version were you running?
In the last updates, we made several improvements in the way the plugin works internally in order to improve performance and reduce the impact in the backend. I would suggest trying the last version of the plugin (0.15.x) and checking if the problems are solved.
If you have access to it, you can use WP-CLI to run Action Scheduler tasks, that would speed-up the generation of reports. That shouldn’t be necessary but might help in really big stores with thousands of orders and products.