I believe the 16-50mm was largely panned as a poor lens with lots of distortion and required a lot of cropping when correcting the profile. I don't have any experience to compare it directly to the rx -100.'
You may want to reconsider the nikonos 15mm. It might actually be a good option for you. at f8, it has great dof (so less fiddling with focussing, etc). you can still leave your camera on aperture priority and get metering to change shutter speed/iso. I think the downside is more likely weight (forward pitch) than settings. 15mm = c. 23mm on full frame equiv whihc would work out well with the subjects you were thinking.
another option would be e-mount 16mm + wide angle converter which is c. 12mm (non fish eye) which would give you 18mm in full frame equiv. the 4.3in dome isn't hard to move around at all.