Skyentific is using NEMA 23 steppers steppers that are rated to have a holding torque of around 200 newton cm. 

But is geared down heavily. The problem I'm facing is that in the size he has linked for the NEMA 23 requires a stepper drive that can produce 2 - 3 amps of current and require a large stepper motor driver. These drivers need to be wired from the RAMPS board to the driver then to the stepper rather than plugging in the stepper driver onto the RAMPS board which is connected to the stepper. Also these bigger drivers can be around 4 times as much to buy compared to the small drivers. Below is a large stepper driver that can supply 4 amps.

Below Is stepper online and it mentions that these motors are suitable for robotic arms!

It also mentions that each stepper motor comes with a data sheet and torque curve. This will be helpful for calculating if my steppers will be powerful enough. Thats when I came across a very informative video series which explains how to choose stepper motors.