NCrypt.exe is the miner. If it is not in task manager its not mining. I did opt-in to mining but I have it turned off right now, Ncrypt is not in tasking. You turn it off, it stays off, even after a computer restart; you have full control over that. If you don't opt-in, I'm not sure if the exe file is even loaded but it will not mine. Based on comments it seems it is loaded. I'm sure is can be disable from Start-up too.
In this case, I don't think Norton was mining on your PC, because the GPU consumption was 0%. Instead, Norton might be performing a scan / removing threats / installing updates.