Google Voice? (and other strictly VoIP services) Absolutely.
I've never had a single problem with Google Fi.
Same, they must mean Google Voice. I've used Google Fi for gosh, 8-9+ years (honestly don't remember, but a good long while) and I've had ZERO problems with anything relating to using it as my cell provider.
Me neither, but I moved a T Mobile number to Fi. It could be different with numbers originally designated to Fi.
I was going to say the same thing. I've been using it close to a decade and I've yet to encounter a circumstance where anything I've used has even seemed aware of the fact that I'm using it rather than a more "traditional" carrier. Conflating both of those would be like saying you need to watch your blood and sugar if you consume a lot of Nestles Crunch bars or Nestle bottled water.