I think pbsurado probably did one looking at its output via a scope, amongst others?
That's great if you like it at 9w, where people get confused is thinking that watts and voltage are different things. I mean they are, but not for your use case. e.g., for your mod at 1.8ohm, 9w is the same as 4V -- when you select 9w, it outputs 4v (or it should). The only reason why using wattage can be nice is that if you have it set to 9w and put in a 2ohm coil with the same eliquid, it'll automatically adjust it to put out 4.2V so you get a similar vape. Otherwise, to get the exact same vape you might have to adjust the voltage up yourself.
However, you can only change the watts in 0.5 steps, while you can change the voltage yourself on those in 0.1 steps. And because variable-wattage is kind of a tacked on feature in these versions, it doesn't always output the voltage you'd think it would.