I own the RX100M3and I love it. it is actually my wife's camera but I am allowed to use it if I "really have to" :-)
Yes, it is a small camera hence the small buttons. If you cant handle it buy the RX10.
The pictures are stunning from that little thing and I bought the time-lapse app for it and it works beautifully. Wouldn't upgrade to the M4 because we don't use it to shoot videos, I got my AX100 for that.
As for HFR recording. Everybody knows that at higher frame rates you need more light and 960fps is quite high, I assume the shutter is 1/2000?
"I own the RX100M4and I love it". Thumbs. :-) Yes, I own the M3 too. Just back from Canada, and very impressed with it. Pics are great. Video from it is good...but I wished I'd taken one of my XA-20's for more control.