I’ve never completely understood this, but I think the answer would probably be “no,” although I’m not sure. Usually when I leave the house I turn off wifi and just use mobile data (this is a habit from my pre-VPN days), although I guess I should probably just keep it on since using strange Wi-Fi with a VPN is ok (unless someone at Starbucks is using the evil twin router trick . . . ?). I was generally under the impression that mobile data is harder to interfere with than Wi-Fi, but I could well be wrong and my notions out of date. So, if need be, please set me straight. 🙂
Your provider will just see encrypted traffic (mostly), so yes it will provide protection.
Only if you trust your VPN service more than your mobile Internet provider.
You forget that nation-states control your ISP. And of course you can choose your VPN provider or run your own.