I don’t know what type of motor combination to use. A blue motor on a 2:1 gear ratio would allow for a speed motor on a torque ratio, while a green motor on a 1:2 gear ratio would allow for a balanced motor on a speed ratio. The blue motor combination wouldn’t be able to push as hard, but the green motor combination would burn out faster, as it is running a speed ratio. So which to pick?
My team uses a 5:3 ratio on 600rpm which has a total rpm of 360. It has a very good balance between speed and pushing power and I would highly recommend it to other teams. Not saying these ratios wouldn’t work but this one seems a lot more efficient.
Because the motor cartridges use gears inside of them to change the output of the motor, they change both the speed and the torque of the motor. The blue cartridges are 600rpm, green 200, and red 100. This means your blue motor combination would actually be slower then your green motor combination, and thus the blue motor one would be stronger then the green motor one.
As for which to pick, it depends on your drivetrain motor count. If you have 6 motors, I would go with around 360-450 rpm, and 200-300rpm for 4 motors. As a general rule of thumb, you want to pick a faster cartridge and gear down from it, as the faster cartridges have less slop and friction.