为什么在国外电量掉得更快，又该怎么控制

Because it is the day the phone has to learn an entire unfamiliar network, often with a stretch where no usable plan is active yet, so the radio searches continuously. It is also usually the day of the most map-reading and looking things up. The two stack, and the effect shows.

If you genuinely are not using it, switching it off helps noticeably, because a SIM that cannot find a network keeps searching. Check first what is tied to that number, such as verification codes by text. If you need those, switch it on in windows rather than leaving it off permanently.

It does not generally throttle the network itself, but it does reduce background activity, so messages and mail may arrive a little later because apps poll less often. What each device trims varies by manufacturer and OS version, so check the list your own settings page shows.

The profile format itself is not the meaningful variable. What changes consumption is how many radios are active at once and the quality of the signal they are holding. Running the home SIM alongside the eSIM while the home SIM has nothing to attach to is what drains the battery, not the fact that it is an eSIM.

It genuinely helps when the room has a weak signal, because the phone stops searching and transmitting all night. If you need to be reachable for calls or messages, weigh that first. A middle path is to charge overnight and disable automatic syncing instead.

Spare battery rules are set by the airline and by each country's authorities. As a general pattern they must be carried in the cabin rather than checked, and capacity limits apply. The specifics differ and change, so check with the airline you are flying before each trip.

It depends on the handset and how you use it. Rather than guess, look up your phone's battery capacity and carry at least one full recharge.

It can help, especially where 5G is weak and the phone keeps switching, but it is not a universal rule. Try it for a day and compare.