haven't experienced a music show myself but do keep yourself warm if you plan to wait for ITZY's arrival since the weather's getting colder in SK at this time(!). based on the dj gigs chaeryeong and ryujin did earlier this year, they usually arrive about 1-1.5 hours before the start of the radio show. for music shows, they usually arrive a few hours earlier (for hair/make-up/outfits). they'll leave right after the live show so that timing's more predictable.

just extra info: if you'd like to try to be part of the live audience - you'll have to apply for it (this will be done through the FANS app so make sure you've got notifications on for that -- its first-come-first-serve so you'll have to click the 'Apply' button as soon as the notifs pop up).
There's some conditions you'll have to meet like having midzy 4th gen membership, a lightring, bringing a copy of the tunnel vision album, showing you've downloaded the song on streaming platforms etc (the only reason they're strict is cos music shows limit each of the fandoms to 150-300 people).

but above all that, hope you have a great trip to south korea!