Generally, Iris comes with almost everything preset for maximum eye health but there are some things you can do to improve the effect of Iris.
Set your monitor Hardware brightness to 100% using your monitor buttons.
This will stop the PWM flicker if your monitor has it.
Iris brightness is automatic and doesn’t use PWM. You don’t need to change anything else.
But if you do need to adjust the brightness to match it to the room lighting you can always do this from the Brightness page.