Hello,
I don't know if your issue is still exists but I had some issues with Eyefinity system with my 7900 XTX on SimRacing games.
I'm running with triple screens 1080p 60Hz (5760*1080) and had some artifacts/lags in game.
The workaround that I've found is to deactivate this Eyefinity system and modify either INI files of simracing games (iRacing-AMS2) or using an external tool to set the correct borderles resolution for ACC.
By following this tuto: https://youtu.be/GExBo7PE6WU?si=L3SZLkXOyl7vqAkk&t=371
It's pretty simple but you need to launch it everytime you want to play on this game and load the file that you generated based on your preference.
No more artifacts or other issues.
I know my issue was not the same as your but maybe to try this way could fix also your problem ;).
Enjoy!