机场 Wi-Fi 和 eSIM，什么时候用哪个

Let the eSIM lead, because it leaves the building with you while airport Wi-Fi does not. Turn off airplane mode and give the phone two or three minutes to register on a network. Then consider the Wi-Fi for the bulky jobs — offline maps, app updates — while you are sitting still.

Almost always because you have not passed that network's login page, which does not always appear by itself. Open a browser and type any plain web address; the portal usually loads instead. If it still does not, forget the network and rejoin. If that fails too, turn Wi-Fi off and use data — do not spend long on it when you still have a journey ahead.

Once the phone is properly on Wi-Fi, traffic goes that way and data use drops a great deal, though some apps and services may still use a little in the background. If you want certainty that nothing runs over data, switch it off while on Wi-Fi — and switch it back on before you walk out of the building, which is the step people most often forget.

It is not a problem if you prepared the eSIM and installed the profile at home, because installation is the only step that needs an internet connection; switching it on at the destination does not. That is the main reason to always install in advance rather than arriving and hoping there is Wi-Fi to do it with.

Technically yes, but if you have data, use it for that kind of task, because it is a connection you control rather than a public one anybody can join. If you must use the Wi-Fi, check that the site is on an encrypted connection, never enter anything on a page that raises a security warning, and sign out properly when you are done.

Not necessarily, but switch off automatic joining so the phone does not attach to networks you did not choose.

A VPN encrypts your traffic but does not remove every risk, such as fake sign-in pages. Still use your own data for sensitive tasks.