How do I choose a motor to operate a rotary switching device?
you want some sort of gear-motor that has enoiugh torque to drive your mechanism.
Note that a classic geneva drive has a large levet on drive side than on the driven side when it's in the middle of the movement.
The internal geneva is the opposite and will probably work better for your task

animated version: https://en.wikipedia.org/wiki/File:Internal_Geneva_wheel_ani.gif
also note that the internal geneva is free-wheeling when the drive pin is in the parked position.
As you only need to rotate 90 degrees your driven wheel only needs two arms.
if you go with a motor whose datasheet torque exceeds the datasheet operating torque of the switch it should work well. When new the motor will likely have more torque and the switch require less, but as they age their performance may decay towards what the datasheet promises. the geneva drive will give a slight torque multiplication which will help too.