Marlin firmware uses the analogWrite function to drive the fan output , which uses 8-bit PWM at 490Hz frequency. Firmware mods are possible that can increase the frequency and/or the resolution by reconfiguring one of the 16 bit timers and writing to the OCR register directly instead of through the analogWrite function. The increase in PWM frequency doesn’t really make a difference with laser engraving from what I’ve seen but the increase in PWM resolution does help with high powered lasers.
I’m using a MKS SBASE board with SmoothieWare firmware for my MPCNC. I think it’s a better fit because it has support for CNC, laser, and 3d printing and DRV8825 stepper drivers. It also has PWM available on a bunch of different pins that support PWM frequencies well above 5Khz.