Some general thoughts, but the TL;DR version is the rig you are looking at seems quite reasonable, though some of your expectations may not be.
Let me just sort of randomly discuss 'classes of UW rigs' a bit, based on my own history.
I started with a disposable underwater film camera. The next trip I had my own digital camera, a Canon point-n-shoot (SD630) in a dedicated Canon housing. (Total cost about $450 new.) I went through a number of Canon point-n-shoots, along with my wife, for several years. SD630, SD870is (first camera i had with IS/VR, which was useful), s95, s120. All were decent, and the newer ones were always a bit better than then older ones.
I eventually hit a wall where I'd taken the shots those cameras were capable of and couldn't really find a way to improve there. Then I added a strobe, which made a huge difference. Then I tried to upgrade with a RX100 ii, Nauticam housing, dual YS-D1 strobes, a focus light, a wet macro lens and a wet wide angle dome. Cost for all that was $5000.
The strobes made a huge difference. Really more important than the camera, within the point-n-shoot class. It's good that you are starting out with a strobe, though that's going to add to the learning curve, and not just photographically. My own (late) wife suffered a ripped eardrum on the 3rd dive of a liveaboard trip in Fiji because she sank down while photographing a Lionfish and not noticing the depth change.
You see once you add a strobe, the rig is no longer something you can simply let go of to dangle from a wrist strap while you use your hands to deal with something underwater. It's much more likely that you will have a rig with two handles that needs to be held about 100% of the time you are in the water with it. That will very much affect a beginning diver. You might try spending some dives without the strobe at first.
As nice as the RX100 was with dual strobes, it was still a point-n-shoot, and it still suffered from AF lag. I got lots of shots of fish tales exiting the frame. It was frustrating, and the following year I spend thousands more to house my D810. I at least could reuse the focus light and strobes.
A DSLR solved my problems. AF was fast and where I wanted it. Dynamic range was awesome. Pixels were everywhere! I could crop (quite a bit). My images were much higher quality.
A DLSR caused a bunch of new problems. First off, the old cameras (like your TG6 idea) had zoom lenses covering a more-or-less normal range. The DSLR (especially full-frame Nikons) pretty much had a 105 macro choice, a 16-35 zoom choice, and a couple of fisheye choices. So much different focal ranges than I was shooting before. Everything became more specialized. Macro ONLY. Wide angle ONLY. Pick before you dive, even before the boat leaves the dock.
And of course the full frame DSLR brought MASSIVE logistic issues, issues you will avoid with a TG6 rig. Hauling around a 230mm dome port has defined how I travel since the day I bought it. This next trip it's going into a Pelican case so I at least no longer have to carry it on. My wide angle dive rig weighs 26 pounds in the dry, by the way. That's just camera, not the carryon or suitcase.
I used the YS-D1 strobes exclusively from 2015 to last summer when I used a loaner Backscatter MF and snoot at the Digital Shootout. I liked it so much I bought a used one, and recently I bought the MF2 with the little plastic gizmo to do remotely-triggered shooting. Let me comment on your strobe options here.
First, the MF2 with snoot for macro. The TG5 and TG6 are well-known as excellent for macro. Partly because the optics are good at it, but also partly because the camera is small enough to get into a lot of tight shooting situations you can't do with a big DSLR rig. You can even use that camera on a selfie stick like a Gopro to get more angles. When shooting macro, the MF/MF2 seems a perfect choice for the TG's. I saw a fair amount of them set up that way at the Digital Shootout. The MF is a somewhat lower-power strobe, but you simply don't need that much power when shooting macros at strobe distances measured in inches. The snoot - skip that for now - is very specialized, and while it works brilliantly, it takes REAL SKILL in buoyancy to aim and use it. It can be extremely frustrating to aim. You have no idea - take my word for it!! Add one after you have another 50 dives in with the camera.
Wide angle is another story. You can't seem to ever have enough strobe power for wide angle, but even if you did, it wouldn't cover more than a few feet of water. Thus you very often end up with mixed strobe and ambient lighting. That's ok if isolating a fish in the water, but not when you have a detail in a coral that runs out of the strobe range. It will either look too red under the strobes, or too green everywhere else. It can be a huge issue, and I find myself mostly just going with ambient when doing wide angle.
Which has this run-on effect. I only want to do wide angle with very clear water, shallow-ish depths and bright sun without clouds. Think 20 foot deep reef shots.
If you shoot like me, you may simply end up not using a strobe when not shooting macro. In which case the MF/MF2 strobe will be fine.
I hedged my bets a bit on my last dive trip. When shooting macro, I would put my MF on one arm and a YS-D1 on the other. The YS-D1 was 'just in case' I needed to shoot something a bit farther away than macro, and/or I wanted some 'fill flash'. I rarely used it.
I 2018 I had been shooting the D810 for three years, and I carried the RX100 as a backup camera. I only used one more time, at a resort in Jamaica. One of my friends asked me to shoot their wedding 're-ceremony' on the beach, and that ceremony took place during the break between dives. I got off the dive boat, had my girlfriend hand my D810, and I proceeded to shoot the ceremony with it. Then I went back to the boat for the 2nd dive. I didn't have time to unhouse/rehouse my D810, so I dove twice with the RX100.
That was interesting for me, because I go to see the best and worst of the RX100 rig right away. The best part was having the normal zoom range again, so I could more easily shoot some subjects. (Turtle was one.) I of course still had the focus lag and point-n-shoot issues (like short battery life). The worst part was the IQ. I had grown used to the flexibility you have when shooting ISO 64 on a 36MP camera. Aside from not being able to crop, nor push and pull shadows and highlights, there was a clear drop-off in lens quality. I hadn't noticed before, but after shooting the DSLR for years it was pretty visibly worse.
So there's your tradeoffs. Some added flexibility over a DSLR/ML, but less IQ at the same time. A normal (slightly wide to a portrait length) zoom, but inability to do real wide angle. Super macro capabilities, but aside from ease in positioning camera, not as good as DSLR macro.
Which is the dilemma in a nutshell: The better the IQ, the less flexibility. The better the IQ, the harder it is to pack and carry. (Size/weight).
The rig you look at will be very good at doing macro, though that also requires excellent buoyancy skills. The flash is perfectly suited to it. I'd suggest leaning into it. Get the rig and shoot macro, then more macro, then some more macro. Do some strobe-less wide angle, and eventually you might either add bigger strobes, or a ML camera that does better wide angle, or maybe just a wet dome port.
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Phoenix Arizona Craig
www.cjcphoto.net
"I miss the days when I was nostalgic."