As far as I know Meta Haptics Studio is currently the only tool for creating .haptic files.
The Xbox controller is sluggish as it has more primitive vibration hardware than the PS5 controller, and currently there is a resource contention issue when multiple hosts are open (i.e, FMOD Studio and Unreal Editor open simultaneously), which makes it even worse- we are hoping to correct this in the next release.
It shouldn’t be waiting for voices to finish though, can you please try reconnecting the controller with just FMOD Studio or just Unreal open and let me know if that improves things at all?