There's no comparison between GR, x100 and m43 bodies in terms of weight and size. The GR feels feather light and is really thin, when the lens is retracted.
I was about to suggest that you buy a pack of cigarettes and rubberband the 17mm to the pack to get a feel for gm1/gm5 size and pocketability, but I see it's too late haha.
I think the lens alone is about the thickness of the GR, or more.
I am like the GR so far, but it's no x100. Very different shooting experience. The 28 f2.8 lens doesn't help if you like bokeh - there's not much of it.