The stepper motors that came with my FT-5 kit say:
Folger Technologies LLC1.8deg 5.0kg/cm 1.5A
on them. Anyone know if I can run these on 24 volts?
That is the correct wiring diagram for the power switch. The ground should be attached to the PSU and chassis.
The short answer is yes.
The longer answer is that the voltage you use for the steppers is dependent on the driver. you then configure the driver to match the stepper. The stepper drivers used on the MKS boards are capable of working at 24v. In fact you will get better stepper performed with 24v.
Note that it is not necessary to use a separate power switch for a mains silicone bed heater. you can use the same switch that powers the PSU. if you do use one switch, you may want to add some inline fuses to provide proper max current protection to each.
Yes you can. It's even better doing so.