Many thanks to all who responded, for your insights and advice.
I'm feeling a bit guilty of bait-and-switch because ultimately I opted for a Sony a6700. It wasn't in my original list because it was more money than I intended to spend. In the end I decided that what was important to me were Sony's reputation for focus and tracking, together with the usability improvements of the a6700. I eased my conscience by buying a low mileage body and a gently-used 18-135mm lens from MPB and trading them the Panasonic 45-150mm, so as not to blow through my budget by too much. I'm looking forward to meeting them both (and hoping I haven't done something dumb).
The Fuji X-S20 came a close second and if I hadn't read so many adverse comments about its autofocus, would likely have won.
Again, thanks for the input; it really was helpful in sorting out my thoughts.