I have the Meikon housing I use with the original RX100 (but the housing currently works for both mark 1 and mark 2 models since the rubber standoffs are a bit flexible). I use the M67 thread for an Inon H100 and a red filter on top of that... no dome. At night, I put a video light (RGBlue system 2) on the cold shoe. I have an Inon macro also, but rarely use it since I'm free diving and don't have the skills yet to steady myself and also have enough breath to play with the focus. Also, as Interceptor regularly points out, threaded lenses are a pain to swap mid-dive. I'd pay whatever extra it is for bayonet adapters if I did it again.
From the few reviews I've seen, the Meikon housing is a bit hit-or-miss as to which if any of the controls will be easy to manipulate. Mine's quite good... I have some trouble with the mode dial, but the mode dial on my RX100 is also quite gummed up and difficult to move even without the housing. Other people have trouble with the focus ring around the lens which could be more of a problem.
I also have an RX100m3 that I'm using for terrestrial use now. I'll probably go with the Meikon housing again.