Danube cruises and the three-capital trip
Many Danube river cruises start or finish in Budapest and stop in Bratislava, Vienna and German towns such as Passau on the way. That is up to four countries in one week, all of them among the 33 in the Europe pack, while the Hungary pack works only in Hungary.
On a cruise, take the Europe pack and size it to how you use the phone ashore: 3 GB for 15 days if you will lean on the ship's wifi, 10 GB for 30 days if you want maps in every port and photos sent home each evening. The same applies to the land version of the trip, Budapest, Bratislava and Vienna by train in a week. Install the eSIM at home before you go; it starts counting at its first connection in any of the covered countries.