The Non OX for almost everyone was a Non-Starter for the sheer requirement of having 3 million baht in a Thai bank.
If you were applying from Sydney prior to them changing over to the evisa system then it was a No-brainer. They were the only consulate that didn’t require funds in Thailand and for $600 was a great option.
Now that they have switched to the evisa system I have no idea if they still offer the upgrade from the OA on application.
their website still states about visa exempt people getting 30 days on entry. That changed in July. Perhaps they don’t pay their website keepers enough to keep current.
Generally speaking if you can get in you’ll get an extension. I’ve only ever seen one case where an extension was refused (where it normally would have been allowed).