I have been using Dyrectory Opus since Amiga times, so far I use it on Windows. I have seen in the forum that many people report problems with the performance of Directory Opus while copying files both locally from drives to USB and over the network. I also have this problem ... The difference in the speed of copying by Directory Opus and Windows Explorer is terrible ... Directory Opus copies on average 3 times slower and additionally the speed is very unstable it ranges from 1 MB / s to max 35 MB / s. I tried to increase the file copy buffer but it doesn't change much ... Has anyone found a way to at least bring the directory Opus copy speed closer to that of Windows Explorer (80-90 MB / s)? My configuration is a computer with an i7 processor, an ax200 network card and an M.2 Western Digital Black SSD, USB Type-C and 3.0, a Router with WIFi AX and a QNAP server with a WD RED 10TB disk ...
The threads you found should have suggestions about changing buffer sizes. Did you try them?
(Also note that if Opus is slow on those devices, almost everything except File Explorer and things using the simple FileCopyEx to copy files from A to B will be slow. Any program reading or writing data to or from memory and those devices will be the same speed, you just won't have noticed it because most programs don't report I/O speed, and the devices are only optimised for FileCopyEx and the one thing that usually reports speed, Explorer, hiding the fact they're slow with everything else.)