Another vote for the 21 mm, which should hold its own very well on that high MP sensor! It is a good thing that the ZF and ZE versions are still available since the Milvus versions add even more bulk to what are already very bulky lenses. I believe the new versions only add better coatings to the lens.
That being said, my ZE version is gathering dust since it was replaced by its smaller and lighter Loxia alter ego, available as a native lens on Sony FE mount. The ZE version was really too bulky and front-heavy when mounted on an adapter. It should however be well balanced on a DSLR in native mount.
21 mm is probably the widest FL which doesn't scream "done with an ultra super-wide lens" at the viewer.
Cheers,
Fabien