Hi Victor, and you have brought up a great point with the Fuji, and I have complained to them in writing several times.
What I believe is happening is that Fuji is over zooming, much like the way the Nikon D800 did and D810, 750 etc. The D850 is the first Nikon I have used that goes to a true 100%. The older Nikon's would go way out beyond a viewable limit and I always had to back the view down 3 times. Never did figure out how to get around that issue but I have been told there is a way to set it to stop where you want. Canon always has given just the 100% or correct view for resolution.
For Live View focus on the GFX, what I do is not double tap like on P1, (which I agree is very elegant in it's workability), but instead use my fingers to zoom into the view like you do on an iPad, iPhone etc. You will find that there is a spot where the image is very sharp and the high rez of the LCD starts to shine. But it's an arbitrary point, and it takes more time than just a quick 2x tap on the screen.
Play back is the same problem (and I use this more than Live View for manual focus), hit play, then double tap and the image displayed is way beyond a 100% real pixel view, again more like a 400% or 300% view. So again I just grow the screen with my fingers, about 1/2 of the amount a 2x tap goes. This shows a very sharp image similar to what you see on the IQ100 at 100%, but again not as easy and it's a non exact method. I just kinda of know how much now to go into the view.
The big difference for me, is the AF on the GFX. Unless you are shooting a very low contrast scene, the AF is quick and accurate, 100% right the first time. I love having multiple AF points, all of which to me are accurate across the frame.
What I do for my work, is I have a function button set for AF, and I leave the camera in MF. So once I hit my subject I know the camera will stay at that focus point, even if you power off the camera. (this was a big improvement over previous Fuji Focus by wire designs). With the joystick and function button, I can quickly locate a spot I want AF to use, hit it and then start my shoot.
The AF on the XF, I don't trust, never have. It's way to long, still reminds me of the older DF+. Again, I am sure many folks love the XF AF, I just find it very lacking. Even with the $850.00 upgrade, and seems to hunt a lot more. But worse it's just one AF point, and I don't want to have to move the camera to reset. For landscape work on the 3100, I just prefer LiveView, simple to move around once zoomed in to 100% and very accurate.
My GFX LCD now seems a bit dim, just may be my older eyes. In bright daylight the LCD even tilted can be hard to read, but the EVF is excellent.
Fuji never has had what I consider quality focus peaking. GFX is a bit better than say a X-T2, but still nothing like the peaking on a Sony A7FII, Nikon D850 (Nikon got it right the first time), or Pentax K1.
Paul C