My system: 3 monitor set up with RX480/8gb Gigabyte reference GPU.
The releases between 18.5.1 and 18.9.1 were a problem for me with mouse lag. 18.9.1 fixed my issues and 18.9.2 seems even better with the Radeon app being more responsive.
Keep in mind that the 18.9.1 release notes reported this issue as fixed so could be you have some other system conflict occurring.
"Cursor or system lag may be observed on some system configurations when two or more displays are connected and one display is powered off."
i have the same problem with all driver above 18.3.1. with 18.9.2 the lag/stuttering also exists but the time between two stutters is longer than with the previous drivers.
i am using an asus rx 570 4g on an asus prime x470 pro on windows 10 home 64 bit.
We continue to investigate this issue which has been resolved for some users with the 18.9.1 driver package.
There is already an extensive thread, please continue your discussion here : https://community.amd.com/message/2879798