By unable to move/delete files, do you mean that it takes much longer than normal? This is what it sounds like from your description of having to wait several minutes for it to complete.

This would be expected if you are running 100% CPU capacity on BOINC--you are essentially having to wait for the commands to move or delete files to be slotted in between a ton of commands for BOINC computation. The more files you have, or the larger they are, the longer you will have to wait for all of the commands to make it through.

A couple of good options to remedy this:
Reduce cores used to to a percentage that will free up one core/thread while you are doing other tasks
Make BOINC a lower priority when you are actively using the machine

There are a couple of other less good options:
Reduce CPU time (this can create large variations in thermal load on the processor)
Suspend BOINC while you are using the machine for other CPU-intensive tasks (you have to remember to resume when done!)

I have no problem moving/deleting/copying files running full speed on my windows 10 pro setup. I can play graphics intensive games as well. I wonder if you are short on memory and therefore swapping out to disk to much. Is your disk activity high? It shouldn't be. If my computer is sluggish I first check out the processes on task master and see what else is running the cpu high or using disk resources. Another thing that might complicate things is if you are having thermal issues.