Hey Ziggy,
Makita Trim Router with 120 Volts sucks 6.25 Amperes, here it would take at least 1.5 mm² / ≙≈AWG15 (2+PE). For For 240 V / EU version of course you only have half the Amperes so a smaller cable would be enough (it’s not the power (Watts) but the current (Amperes) that gives a wire’s cross-section area).
Steppers in the Onefinity, if they suck about 3 Amperes (do they?), here 0.75 mm² ≙≈AWG 18 would be enough. But the controller provides up to 6 A for each motor, so in case of retrofitting a stronger stepper motor I also would take at least 1.5 mm² / ≙≈AWG15. Here 4 wires are enough, shield to chassis, of course a 5th wire to ground can do no harm.
Note that I’ve seen that often suppliers especially web shops for consumers choose wire strength at the lower limit. But if you calculate the wire strength and you are between two wire gauges, you got to always take the next-higher wire strength.