Doubt in choosing the right DC motor? Take this motor as an example - https://www.robotshop.com/en/12v-100rpm-583-oz-in-brushed-dc-motor.html

it has torque of 42kg.cm

I know all the calculation to find the payload of dc motor from here - https://www.quora.com/How-do-I-calculate-how-much-weight-can-DC-motor-carry

My main concern is the output power. Power formula is:-

power = voltage x Stall Current
      = 12 x 2A = 24W

But the specification says that the power is 5W. Which value should I use in my calculation?
With a current rating of 0.68 A at 12 V you get the normal power requirement of 8.6 W for a 7Kg.cm torque.

If, for any reason, you stall the motor, your driver must be capable to output 2.2 A or 26.5 W to avoid a permanent damage.