While the app can handle multiple concurrent edit tasks (and rollback tasks) we do not recommend them:
1. Confusion regarding the item prices due to multiple tasks editing the same product.
2. Limitations of the Shopify API.
On average it takes about 1 second to update 2 items. This is just an estimate. The actual speed could be slightly different based on the number of products that you update and your Shopify plan API limit.
If you execute multiple tasks simultaneously, then for each task the app not be able to update 2 items in a sec. It will be much slower. This is because of the limitation of the Shopify API. So you will get a feeling that the tasks are stuck. Instead, if you schedule the price edit tasks (or rollback) for each of your product groupings one after the other, then it will be more efficient.
The app will pause a new task if 3 tasks are already running in parallel. Later you can evaluate and restart the paused tasks.
Note: In case if you schedule price edit tasks (and rollbacks) at the same time, then the tasks will be executed alright, but with a significantly longer time.