Most travelers overbuy because they guess from home data use. Travel days are different.
Light use
Maps, chat, and email with hotel Wi-Fi at night often stay under 500 MB a day. A 5 GB plan covers a week of that pattern.
Everyday travel
Ride apps, translation, and a few photo uploads land closer to 1 GB a day. A 10 GB plan is the safer default for a 7 to 10 day trip.
When unlimited makes sense
Pick unlimited if you navigate all day, hotspot a laptop, or stream. Read the fair-use note on the plan: high speed may step down after a set allowance.