Cannot control the power intensity, any ideas?

Commanding high engraving speeds will cause the engraver to engrave at its maximum speed and then reduce power to compensate for the unavailable speed.

Which speed and power settings are you testing with.

There are additional settings in GRBL that are ‘Constant power’.

For a Sculpfun S30 we’re expecting a Variable speed shown in the Build options as a ‘V’.

Please request the following reports from your Sculpfun S30.
In LightBurn, in the Console window, type the following,
$i
$$
pressing enter after each one.
Please copy and paste the whole works into a reply here.
We’ll be able to see how the Sculpfun is set up and what the spindle (laser) control is expecting. (along with the maximum allowed speeds)