Almost all your questions depend on the reduction gearing presented by the threaded rod drive.
Speed, torque and other variables will contribute the selection of motor, or motor and (another) reduction gearbox.
At first glance, i’d be looking at simple DC motors, with limit switches.
Keep in mind (depending on gearing),that there will be some overrun when the motor is stopped at the limits of travel.
3-5 Kg plus the platform isn’t much if you have a 10:1 reduction, and i’d probably allow double that as a designed load.