Very nice setup!
I have the 18-270 and I agree it's not the best lens optically - but then, a consumer zoom covering such a wide range of focal lengths is always going to be very much a compromise. The biggest problem with it, in my view, is a tendency to create small donuts on specular highlights in the bokeh (my Panasonic TZ70 compact does the same thing). That said, with careful subject placement, it can also produce wonderfully smooth bokeh (see attached pic).
That Vello flash bracket is interesting - how heavy is it? It looks like it could get in the way of the grip when in portrait mode, though, or am I mistaken? Right now, if I'm going to be swapping between landscape and portrait, I attach the flash via a cable and hold it in my left hand. It's not ideal.
Oh, and I have to say, those are impressive photos - nicely done!