I have used the Nauticam 7D and 7D MkII housings. I also used an Aquatica 7D housing for a few months during the changeover from Subal to Nauticam. It had very good handles and I didn't miss having a hand strap while using it.
I used a few different Subal housings over the years (1 x film, 1 x digital and 2 x dSLR housings) and found their hand straps essential as their handles weren't very good and a hand strap was needed to operate the housing one handed. When I switched over to Nauticam housings (i'm on my second one now) I thought that not having a hand strap would be a huge problem. However, I found that I don't need one to use the Nauticam housings one handed and have never missed having one.
The suggested filter absorbs ~20% of light, this sounds counterproductive
Inon do two versions of their warming filter, a clear version which does not affect strobe output (and has a 100° beam angle) and a diffuser version which reduces output by 0.5 EV (and has a beam angle of 110°. If you go this way you want the 4600K version, specifications of both versions for the Z240 are at the bottom of this page: