What would happen if I put a voltage of 12 volts onto the power in connector to drive 12 volts servos. Obviously still driving the PWM Supply Voltage with between 3.3v-5v.
Some other suppliers of (PCA 9685) boards can handle it.
I geuss PCA 9685 works up to 6V only. I use it for a robotic arm, and I read something like that when I bought it, but it has been a year ago, so better to look after in its specification.
The other boards you mention probably have an isolated servo power rail. You can wire an isolated power rail yourself for boards that do not have an isolated servo power input. If you do this wrong you will fry the driver board so don’t do it unless you understand using multiple common ground power supplies. Wire the 12V servo power GROUND and the PWM signal ground together. This should be done with a single wire connecting the Grove driver board ground to the servo power ground. IMPORTANT! Then DISCONNECT the red power wire from all the 12V servo connectors and run them to the positive on the separate 12V servo power supply. For each of the PWM outputs run to a 12V servo the center pin on the driver board will be connected to nothing. Do not wire the positive from the servo power to the driver board in any way or you will fry it!