It's just a bridge camera with a cropped 1" sensor, and the price is quite expensive --- more than any entry level interchange lenses system digital cameras, I don't even believe I will buy it at the time it was out, but I did.
The performance of the lens at the tele end (600mm F4.0, comparatively to 35mm standard) is stunning, the resolution of the 20mp is very good, the picture quality is still acceptable when I cropped it by half.
It isn't heavy to carry, it's 24mm-600mm will cover most scenario, but if you want to track little birds in flight or better macro photos, get the mark 4 instead.
After I have got it, I left my A7R2 and lenses collecting dust at home.

I have the RX10 which "only" has the 200mm lens. I bought it to videotape lectures from the back of a dimly lit hall. I bought the RX10 because it had the 1" sensor and the 2.8 all the way 200mm lens. I use a Panasonic MDH1 which runs for four hours on wide angle to handle the sound and cut-outs. I use the RX10 to video in HD and use it for the close up work. Its 2.8 200mm lens and 1" sensor produce a good image and I use the Panasonic to cover for the times when I have to reset the RX10 every 29 minutes. The RX10 is a really solid camera which has an excellent viewfinder and takes excellent video and photos. A bit expensive but worth it. I do not need the extra features of the RX10 III - yet.

I've owned a few cameras but none with the sheer versatility of having a fast f/2.4-4.0 24-600mm lens! The zoom is just amazing and is a game changer as the lens is tack sharp both wide open and telephoto. The 1" sensor gives great performance far better then many larger sensors even in lower lighting and the camera offers amazing 4k video that looks as good as anything out there. There is also a super slow motion mode that can go up to 1000 fps but gives great results up to around half that. If you could have only one camera this would be it.