So I spent a lot of time trying to get G-Sync to work in borderless windows for FFXIV. I know it works in fullscreen but I have multiple monitor setup so I need to run it in borderless. I was about to give up until I found a thread on Steam about Windows 11 new feature that forces older games to use the new flip model that enables g-sync for older games. I tried it and it works.

Not sure about posting links rule on this forum so I'm just reposting here just incase there are other people like me that can't get g-sync to work with borderless windows.

The sad thing is that this solution only works on Windows 11.

Here are the steps for it:
1. Open Settings
2. Go to System
3. Click on Display
4. Scroll down to Graphics and click that
5. Right under Default Settings there should be "Change default graphic settings", click that
6. Enable "Optimizations for windowed games"

And you're done! Enjoy your variable refresh rate with borderless windows.