VoLTE! There is Hope!!
So after installing the 1908.25 update on my North American (not Tencent) 512/12GB ROG2, and did a full wipe/reset, this popped up under my SIM1 options!!! I had not seen that until I did the reset post update.
Looks like I need to run a 2nd SIM card though, which I just happen to have (data sharing sim in my tablet) which I can use to try this! I'll try later this afternoon when I am home from work and report back
For those wondering, I am in Australia, and on the Vodafone network