I think that there is some problem between WD software and USB 3.0 standard explorer copy files from disk inside laptop to external disk. Performance is oscillating from 20 to 40 mb/s. Before installing WD software it was around 90 mb/s on same disks with large files. I have i5-8265u laptop. On desktop and AMD platform everything is OK. Hope that I am not wrong, and that it is not some other problem.
You can try to uninstall the software and install it again to check whether the issue is caused by the software.
Sorry, my laptop died slowly.