Oh, you have both now? I am also considering the GX9 and it looks to be pretty much the same as the GX85 size wise. I am mostly a holiday photographer and maybe will use it for events with family and friends. As such, I think the G9 may be a bit of an overkill. It would be interesting to learn from your experience using both the GX85 and the G9.
For me, my gx85 is pretty much my go-to camera for holidays at first-time destinations. I may or may not bring the G9 for subsequent visits, depending on how safe I feel the place is and if there's a need to (Japan is definitely a must haha!).
The G9 primary use would be for mtb events that I often cover; Can't tell you how many times I got frustrated at not being able to tilt the screen at a low-angle, portrait mode.