I've had unlocked on VZ for both the S9 and now my S10. Wifi calling can be enabled/disabled on the S10 ( i.e. there is an actual toggle for it in Settings). I'm not sure what a previous poster indicated about "flashing" the phone. Sure you can root it if you want, but why? To put VZs bloatware back on the phone? Each time I've received my new unlocked phone, I take the VZ sim out of the old phone, put in the new one, and I am up and running in less than 60 seconds on the VZ network. Google automatically begins restoring my contacts, the APP Store knows every app I had on my old phone and I can actually use this moment not to add back anything I really didn't use before. I did add a Voice Mail app, but that was the only change from a locked phone.
Buying an unlocked phone is not rocket science and I was certainly nervous the first time a couple of years ago. The sim card controls network access and technically if you had accounts and sim cards from VZ, ATT and T-MO you could just bounce between carriers all day long by swapping out cards on an unlocked phone.
I'm not sure there are any big revelations using unlocked vs locked, I just like the "perception" of freedom to able to switch carriers and the lack of VZ bloatware.