Hi
My daughter recently received these two items and would like to use the CE functionality.
She is currently with Amaysim and pays $15 per month and gets 18gb in data.
I believe at the moment only Telstra , Optus and Vodafone offer the service and they are pretty pricey.
Thanks
https://www.amaysim.com.au/plans/esim/
Some of their MVNO's are now providing eSIM. Woolworths, Kogan, GOMO and amaysim now have esim options.
For apple LTE watches, you must use a post-paid plan and then sign up to a smartwatch plan which is an extra $5 or $10 a month, depending on the offer.
https://www.ozbargain.com.au/node/734252
This will significantly increase the amount you have to spend a month, so consider strongly whether you want or need to have calling capability on your smartwatch. Most people don't.