I am currently waiting for a work Visa P-1. But I want to visit friends and holiday in US before I start work. Can I enter on ESTA/VWP and holiday for 3 months whilst waiting for visa process, return home to Australia to collect the visa, and then start work in the US?
It certainly is possible. However you might undergo additional scrutiny at immigration in the US and need to overcome suspicion that you're trying to work before your authorization begins.
How likely and severe that scrutiny is, will be up to the officer you happen to meet, his mood and your performance. If you have already used your ESTA before, some airports allow you to enter via automatic terminals, which would then likely spare you an interview.
If interviewed you should follow the basic rules to be upfront about everything on the one hand but on the other hand not to sponsor too much information. I guess if you have a tourist itinerary with return flight booked, accomodation and other plans, that should go down well with the officer. Also if you can somehow show that the gig you need the P1 visa for is not a thing yet at the time of your visit, there would be even less reason for concern.