When an HDD or SD mounted, the transfer speed is very slow: copying a file from my computer to the HDD or SD is only 2.9MByte / second, slower than a wi-fi 4 connection.
My computer is connected over a wi-fi 5 connection to the main router and the main router wired to the Filehub. For comparision, transferring over wifi from computer to smartphone or tablet is 15-20 MByte / second, both connected over wi-fi 5.
All the RAVpower devices...for the CPU...this speed seems normal.
(BTW...you never tell us the exact make/model of the device, I had to glean that info from the other post you linked, which also doesn't include the specific device name as listed on the Wiki...it helped I browsed here from that thread. )
Perhaps in the future, you shouldn't make such major edits to the original posting.
(Again, I only understood what this means because I browsed here from the previous thread...and read some of your post revisions.)