Hello!!
Possibly a little bit outdated, but I have just discovered this forum.
I own a X-T3 housed in a Nauticam housing for nine months now.
Until now my only experience is with the 80mm macro, (actually it is my only underwater photography experience) and I have to say that I am very happy with the system.
The usability of the camera in the Nauticam housing is very good, and I have no complaints about it.
The X-T3 + 80mm macro behaves very well underwater, the focus is fast and quite accurate.
No complaints about the image quality too, provided I stay bellow f16, due to refraction.
I have no experience on the wide angle area, but I plan to experiment with the MWL-1 soon.
Any other questions under my knowledge will be happily answered.
Best Regards!!