I had the GR as only digital camera while in NYC couple of weeks ago and last weekend while in Waterton NP I had the X100 w/ GW3 and Tele-converter lens with me, they are great little cameras but here's why I think they are not the perfect vacation camera compared to the Q.
the GR is very small and discrete, perfect for street photography in NYC and I always had it set to 35mm crop, however to me it's not fun to shoot with outside of street photography
the X100 family is great, fun to shoot with its rangefinder like body, has a wide and tele converter lens but they are not exactly small, fast and easy to mount on the camera.
if you have a UV filter on the 35mm lens, you have to unscrew the adapter, screw the converter lens and finally turn the conversion settings on the menu, now if you have to continuously change between focal lengths, this can get ugly really quickly.
also the X100 lens and the WCL-X100 takes 49mm filter while the TCL-X100 takes 67mm
the Q on the other hand feels like a RF camera which means fun to shoot with for me and can crop to 35mm(16MP?) or 50mm(8MP?) with a push of a button without having to fool around with converter lens.
sure the lens might be a little too big but I will be most likely walking with the camera on a strap.
these are just my observations based from my experience with the GR and X100 and what I've seen from the Q reviews, so who knows, I might change my mind once I hold a Q in my hands. my backup plan is to get a X100T instead (GR for 21mm, 28mm and 35mm and X100T for 50mm)