I will give another summary based on my experiences in down sizing over the years......
Macro and SUPER Macro as a prime interest? The Olympus TG-6 is pretty stellar even shooting the camera's little built in flash with several prize winners in big contests to prove it for that purpose.
General shooting like fish, dive buddies and wide angle shots - Either a Sony RX100 VA or VII or Canon G7X II / III choices. You can add lower cost wide angle wet lenses to these and have flexibility in a larger 1" sensor than the Olympus TG-6.
Housings - If set on aluminum yes, Nauticam is great but Marelux recently debuted new compact housings for the Olympus TG-6 and Sony RX100 VII. I used a Sony RX100 VII in a Fantasea housing for whales in Moorea plus my tried and true Canon G7X II in a Fantasea housing which I still own.
Many only want a metal housing. For me after 1,000 + dives using Fantasea housings all over the world I think they're fine.
The Olympus branded TG-6 housing (PT-59) is made by AOI in China same factory as Fantasea housings. Only drawback to the Olympus PT-59 housing is it has a single back o-ring where Fantasea have 2 o-rings. I don't think the PT-59 housing hasn't been updated to a vacuum system option like on the newest Fantasea housings.
Last choice is strobe(s) or maybe a video light.
Strobe lit pics for stills have punch to them but you'll need more NIMH batteries, charger, tray, arm, optical cord(s), etc. I've shot with one single small Inon S2000 strobe mounted on my Fantasy housing's cold shoe and no tray and was happy with pictures I produced.
Being extremely lazy and wanting to enjoy my dives I continually look for how to take less in the water and travel with so there's that consideration.
Jason Bourne in those movies saves the world traveling with a small gym bag and is my hero
Good luck on your choices!
David Haas