在国外开车，导航流量怎么准备

No, provided you downloaded the map for that area. Turn-by-turn guidance and your position on the map work without data, because GPS is a satellite signal the phone simply receives. What you lose without data is live traffic and automatic rerouting around congestion.

The right size comes from your ordinary usage habits, not from the distance you will cover, because navigation is light on data once the maps are downloaded. Estimate from what you do on a normal day, such as messaging, evening video and photo uploads, then multiply by the number of days. The data calculator on the site gives a reasonable starting figure.

Those systems project your phone onto the car's screen, so they use whatever connection the phone has, whether that comes from an eSIM or a physical SIM. What to verify is that the line set as your data line is the trip profile, and that the particular car supports the system, which varies by model.

Lower the screen brightness, close what is running in the background, and if there is a second phone in the car move navigation to it before the first one dies. With no charger available, switch the screen off and follow the spoken directions only, which uses far less power than a lit display.

Not necessarily. If your phone can share a hotspot and the plan allows it, the tablet can ride on the same connection. Check two things first: the plan's hotspot terms, and whether that tablet model supports eSIM at all if you would rather give it its own connection.

Yes, in the major map apps if you downloaded that area. What is missing is live traffic and automatic rerouting around congestion.

Navigation itself uses little data when maps are downloaded. The size is decided by your ordinary other use, so estimate from behaviour rather than distance.