I'm able to launch the game but if I move my mouse diagonally it completely tanks the FPS. It is making the game unplayable since every time I try to look around I start to drop to single digit frames.

Here's a couple videos showing it -

https://www.youtube.com/watch?v=xqdOxwgSI4A

https://www.youtube.com/watch?v=Fk2Kj6dwCHg

In the 2nd video you can see that I am running in Windowed mode, I have turned my refresh rate down to 60 (from 144). It only drops the frames when I move my mouse in-game when it is the active window.

I've tried clearing my user settings, I've tried turning my graphics down, using the OS cursor instead of the FFXIV one. I completely reinstalled the game cleanly and it didn't change anything.

Any help would be much appreciated. I can't play the game when it's doing this.

Specs:

Mac mini 2018
i7 6-Cores 3.2GHz
32GB Memory
Razer Core X eGPU with a RX 590
macOS Catalina (fully updated)