I've always used thumb grips with the X100F (T,S,0) since it improves the grip tremendously. When I use the hotshoe however, the grip must be removed and once again I return to a hard to grip camera. When I was in Japan, I bought a sheet of camera leather tape in a hobby store. I didn't think much of it then but it became useful very quickly as I started using it on many parts of the camera.
Flash is harsh, direct, raw, and is something I will use only when I want these qualities. For soft, emotive, moody lighting I would often go with available light. Even so, often the available lights cannot really create the kind of look one would want without any modifications. In my kit I carry 3 LED lights with me, 2 of them being small panels and one being a tube.