Just as an FYI: One benefit of the GFX line is you get to keep leaf shutter flash sync ability (at 1/800s) using any Hassy H series lens with the Fuji adapter.
Push a button on the adapter to switch between focal or leaf shutter. Use H lens w/ focal shutter, you save wear & tear on the lens shutter and HSS works fine. Pop to leaf shutter and you get 1/800 sync. Fuji TTL works in either case.
We ran a GFX50S and H5D side by side for a year and the H adapter works brilliantly. Only downsides are MF only (if that's a downside for you) - and it's stop-down metering. Unlike when on a X_D body, on the GFX when you stop down the H lens via the command dial, it does it immediately and you need auto EFV gain to focus accurately.