Germany, France, and another Rhine River Country, with T Mobile Family Plan and VPN Question

[Microman]

I already know that I can use text and data in these countries with my 7 member family plan.

And phone calls could be xx cents a minute, which I will try to avoid.

What should I do, AIRPLANE mode, or ? Wifi will be available on this river cruise.

And Have PIA VPN at home on my MacBook, can I or should I try and use the VPN on the iPhone as well?