I read the gcode (of E2 engraving test ), but I didn’t find indication about the PWM (only a M5 code at the end ??)
The laser strength can be controlled by inline codes. It uses the ‘S’ parameter in the G0, G1, G2, and G3 codes. Full power PWM is 255, so if you look at this line in the file you used:
G1 X34.01 F3180 S70
…you see ‘S70’ The laser is set at 70/255 power…roughly 27% power. In addition, M3 and M5 should also work, plus M42 works to directly turn the pin on and off. I don’t think the Fusion 360 post processor supports inline laser PWM codes.
I second @Olijouve touting of LightBurn. I frequently using Fusion 360 for my design work, but export the finished pieces as DXF files and do the cutting in LightBurn. LightBurn does support inline commands.
I’m not sure it makes any difference for laser cutting, but Don Gamble has made significant improvements to the Fusion 360 Guffy post processor. You can find a link to his latest release here.