A 2 ohm coil is a good start for the Twist. Be aware that lower resistances and small
batteries can put you into a range where the voltage you get may be lower than what your Twist is set for due to limitations in the electronics. It will scale back the actual voltage to prevent going over its preprogrammed current limit of 2.5 or 3 amps, depending on the model.
You should be fine at 1.8 to 2 ohms.