Shutter Speed setting on Olympus Tg-6 with Fcon t01

My settings are based on experience with a Sony point-n-shoot followed by a D810 and a D850.

When I first got my Sony RX100 II, with dual strobes, I pretty much set things on auto or aperture-priority and went diving.   Got well-exposed blurry shots of fish tails swimming out of frame at 1/30th of a second.

I could tell this during the first dive, and I was immediately frustrated by the slow shutter speeds.   Looking for a 'right now' solution, I changed to shutter priority and ended up at 1/160th as a compromise speed.

1/160th - slower and I get blurry fish.   Faster and I start running into sync issues with the DSLRs, and of course I lose dynamic range as the ISO climbs.  Occasionally I'd dial back to 1/120th, but 1/160th seems to be the 'golden speed' of compromise.

On the RX100, I think I eventually set it to manual mode, set ISO to a max of 400, and played with strobe power.

On my Nikons I shoot much the same way, and in particular I still set a shutter speed of 1/160th, sometimes 1/200th.   My max sync speed with the YS-D1 strobes is right around 1/200th even though my shutter will sync at 1/320th.   The strobes just don't fire fast enough to avoid a black shadow across one side of the frame.

You have competing issues here.   You need a fast shutter speed, but at the same time you need the lowest ISO you can live with, especially if you are doing a lot of post-processing.   Ultimately you need to control the lighting with powerful strobes used within their range.

Over the years of post-processing underwater images from my Nikons, I've come to really try hard to shoot at base ISO (64 for me) because that gives me incredible dynamic range to work with.   Closest thing to medium format to this ancient photographer's experience.