I'm using Oly EM5III with following accessories:
Lens: 7-14, 12-40, 30 Macro, 60 Macro, and a wet dioptor lens (+10, if I recall correctly)
Housing: Ikelite Housing for EM5III, 6in" dome port with extension (for 7-14 and 12-40), Flat port for 30 Macro, Flat port with extension (same one use for wide setup) for 60 Macro
Light: Ikelite DS-161 (about 10yrs old) and DS-162. Connection using Ikelite TTL convertor unit and dual Sync chord.
Tray & Arm: Generic brand that I found on local online shopping store - delivery origin from somewhere in China
I'd usually set camera to M (manual) mode, Speed 1/250 (max sync speed), Aperture f/8. Strobe set to "Fill-in" to make the strobe fired on every shot. Then I set the two Ikelite Strobe on "TTL". Camera flash RC mode to "off". (this is as recommended by Ikelite - if you use fiber optic connection flash setting may be different)
Then I shoot, and may be lower speed if I want more background light, or have wider/smaller aperture to control foreground (strobe) light. ISO typically set to 200.
Also, I'd set AE-L/AF-L butting for "back button focus. compensation button (right-front) to Whitebalance - this is to allow for quick custom whitebalance. I'd do a custom white balance on a sand patch at a couple of depth, stored them separately as custom 1,2,3.
LCD display set "Liveview boost" to on. Turn off the proximity sensor for the EVF (as the back of the housing make the sensor think that it's always at eye-level)
Also, set the arrow pad at the back to allow to use them for shutter/aperture control. (Can't recall what's the function is called) I prefer this as it's easier than turning the knob for the top dial on my housing.
If shooting macro/supermacro, I might adjust flash compensation to lower value.