It's been a while since I used XCP for that, but when I did [1] I logged its actions and kept the log.
The use case for this was that the operator had to produce a cryptographically verifiable report of their actions. In the video that's towards the very end when the log is signed by PGP.
Don't know about defining the threads. I'd observe the number of deletes per second and use multiple XCP nodes if one is not enough.