lairdb,
As hsinhai says STTL on Inon strobes works very good. On the beautifully small Inon S2000 you can leave the top center triangular shaped control in B (middle STTL output) and then dial a bit of over / under FLASH output easier by adjusting the camera's flash. I do this with my Canon G7X II with a MY MENU tab you can save frequently used adjustments.
The 3 shots included above were all shot on STTL including the manta at night in the Maldives!)
The only down side shooting STTL is your camera battery will last maybe 125 -150 shots depending on how close you are to your subject and f-stop you choose.
Shoot too far away and not fill the frame with something the flash output can "bounce" off back to your camera. That causes your camera's flash to "quench" and decrease the output to not overexpose the shot. Shoot too far away or close the f-stop too much and your camera flash may dump a FULL power flash each shot
I've also experimented with manual settings. On my Canon G7X II I dial down my flash in a MENU to 1/3 with no "pre-flash" output. This give much faster recycle time between shots plus more shots per camera battery.
You then MANUALLY select a power output on your Inon strobe. Do some test shots at 2', 3' nd maximum maybe 4' away.
Pre-setting shutter speed, f-stop and ISO I then adjust one parameter, ISO resulting in a faster adjustment than playing with strobe power adjustments.
I still use both STTL and manual flash and Inon strobes give you the capability to do so!
Just one old guy's opinion
David Haas
Haas Photography Inc.