When we go to Oz we take cash but we have also taken a card with money already on it and use it like a debit card,saves carting a load of cash round with you.
Don't, use a credit card. I have the Halifax Clarity. Been to Australia 5 times since 2016. Don't take more than a hundred dollars in cash and get that from the Post Office or wherever. Get a credit card. https://www.moneysavingexpert.com/credit-cards/travel-credit-cards/ I have the Halifax Clarity but apparently there's a better one that's been released since this one.
Last time i was in Oz / Hong Kong i took a sall amount of cash together with my Revolut Card , Load the card with money from your bank account , use the app on your phone to covert to local currency as & when required.
From watching the boarder patrol programmes they don't seem to like you carrying too much cash We use the Caxton FX card, you can load it from you phone on the app and use it like a debit card
I took small amount of cash plus a travel card loaded before I travelled which I was advised to. Be careful not to carry too much cash,their pretty keen. Enjoy your travels and don't forget the Barnsley war cry at the bar aaaaaaar much.
Another vote for the Halifax Clarity credit card. No fees, almost perfect exchange rate, no interest on purchases (except cash) if you pay in full each month, and 0.5% cash back from time to time.
Monzo/Starling debit card for day-to-day use. Halifax Clarity/Santander for fee-free larger purchases that you might not want to immediately stump up for.