I have a 1TB 870 QVO and my write speeds are dramatically slower than any of my other SSDs.
DriveDX gives the SSD a clean bill of health and 99% Life Remaining. Reads are averaging 428 MB/s through an iMac USB 3 port, but writes are averaging 118 MB/s!!! This is 250 MB/s below the next slowest SSD!!!
Did you resolve this issue yourself? I have exactly the same drive with pretty much the same issue. Read about 550mb/s and write only around 85mb/s