I run an SKR Pro on 24V, and another on 12V.
For things like limit switches, and motors, there are zero changes required. The limit switches run on 5V, and the motors run at whatever the set current rating is.
The only difference, wring wise, will be if you are running fans or LEDs that need 12V, which you’ll need th either provide a separate 12V source for, or else change to 24V devices.
If you run 12V fans for anything, all you really need to do is use a voltage converter. Tie the grounds together, and swap out the positive pin on the fans for the 12V source. Use the on-board pin for the negative (This is where the PWM and/or switch on/off happens)
Edit: I should add that there are practically no advantages to running at 24V for a CNC machine. The only thing that it allows is somewhat faster motor speed, but we should never exceed the capabilities of 12V operation while pushing around a router or spindle.