I'd definitely want Power for an audax I wanted to do well in. I pace a million times better With it.
I'm not so bothered for short stuff. Then its just. Smash yourself to make the Group at the start. Ride at their pace, finish according to how much you have left in the tank.
Audax is about eating not pacing. Aud in French means "food" and "ax" means "face". The reasoning being to succeed you need to stuff as much food into your face as possible. Everything else just happens. Pedal, eat, sleep in required. Repeat until Arrivee.
Are you going for a time then? (e.g. sub 60h?) Otherwise a coach, or even training with power, is a bit of overkill for an Audax.