if I need different Mosfet or different logic?
I use the 12-bit PWM from a PCA9685 for my LED lighting.Dims down to very low brightness.Leo..
The LED PWM Controller is designed primarily to drive LEDs. It provides a wide resolution for PWM duty cycle settings. For instance, the PWM frequency of 5 kHz can have the maximum duty resolution of 13 bits. It means that the duty can be set anywhere from 0 to 100% with a resolution of ~0.012% (2 ** 13 = 8192 discrete levels of the LED intensity).https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/ledc.html
Most of the time, you are doing something wrong if you think you need a Mega 2560.Expander boards like the PCA9685 will handle lots of input and output, often performing the buffering you need for higher currents and multiplexing. Only for very complex code not involving WiFi might you need the extra code memory on the Mega 2560.12 bit PWM is probably enough.