I think the pinout follows this convention:
Yes if the encoder is attached to the motor, the hall sensors will be redundant, at least once the encoder is calibrated against the motor. I guess if you are using an encoder without index pulse, the hall pulses could help with calibration; but I think an encoder with index pulse will be better.
Yes the torque should be given by this forumla:
8.27 * motor_current / kv. That means for higher torque you want high allowed motor current, and low kv. On your the product page of your considered motors they don’t specify a current spec, so it’s hard to compare. If in doubt, just get the lowest kv motor of the same size.