im not sure on those, it probably better to just buy what ever amounts you are wanting and build your BTC position in your own self custodial wallet ( like a Trezor wallet or a Ledger wallet , i use a Ledger Nano s and never had a issue ) but if you are just starting to get into it all then i can understand why you would rather go for the easy route and get exposure through the ASX.
if wanting to use a exchange u have a few options but very limited, i have been using swyftx and coinspot , but there is some important things you would need to educate your self on when it comes to being self custodial and using a trezor / ledger wallet. i would recommended when u have free time to do abit of reading about and and get familiar with the idea of these kind of wallets , dont just go blindly into it not knowing how to use it because thats how people make mistakes and then they blame the device when its a human error , its very simple when you get the hang of it but like i said, there are some important things you need to read about before getting deep into it, Seed phrase , keeping it protected , etc.
Then again you could always just hold the BTC on the exchange but if its a big chunk of money / long term position you are building, Cold wallet ( trezor / ledger ) is always recommended
