The displayed content looks weird in the desktop app (weird lines in content / blurry content) / My mouse cursor disappears

This is most likely due to a setting called "Hardware Acceleration".
This can be fixed very easily by disabling the Hardware Acceleration option in Overwolf. To do so, open the Overwolf app on your PC, then go to settings, then, in the "General" tab, disable the "Hardware Acceleration" checkbox. Then reboot your PC