2dm VoWifi battery drain - experiences?

We have rather poor cellular coverage across all three major networks, despite living in an urban area.

Some very general measurements from the cell phones across two of the networks report that we receive a 2dm signal of -113dBm, while Spark is a bit better at -104dBm, both however are call dropping & battery sapping bad.

Migrating to 2dm and using VoWifi might be a solution, however some have stated to me that their battery life has been poor. We are using SGS 10+ phones but most who have stated they have battery issues, were iPhone users. I'm not sure of the accuracy of these battery issue complaints, so I'm wondering:

1. What you've experienced, and

2. Whether you routinely use airplane mode with wifi enabled while at home to save battery power a little bit further?

Thanks in advance.