Physical SIM or eSIM?

Either works; eSIM avoids kiosk lines if your phone is unlocked and eSIM-capable.

Do I need voice calls?

Data + Wi-Fi calling often suffice; keep voice if your hotel or tour needs local callbacks.

Travel tech · 콘서트 주간 한국 eSIM — 데이터·OTP·티켓 앱

Korea-eSIM für die Konzertwoche

Install and enable the eSIM before leaving Wi-Fi at home; airport Wi-Fi is a backup only.
Some ticketing apps still want a Korean +82 number — memberships bought earlier beat day-of hacks.
Download offline Kakao/Naver map areas for KSPO, Gocheok, and KINTEX corridors.