Thank you for the reply jjajja. We apologize for the delay in our response.

In regards to the error you get while trying to run in DirectX 9 mode, try setting your desktop resolution to something lower than it's native pixel count (such as 900p), then try to launch the game in Fullscreen mode. Does the error still occur? Try using borderless windowed with this lowered resolution and see if this has any affect on the performance.

We hope we can be of assistance in helping you enjoy the exciting world of Final Fantasy XIV!