We can't tell you what GTA 6's launch-day experience will be. We can tell you what Rockstar's pattern has been across recent releases and what to look for.
This is editorial reading, not a strategy guide. For the broader regions, see the regions explainer.
What the in-game map will probably look like
Mostly fogged. Rockstar's recent games (GTA V, RDR2) start with the map mostly hidden and reveal it as the player visits each region. Expect Vice City to be partially revealed at game start (story-driven) and the rest of Leonida to fog out.
Story progression will reveal regions gradually. By the end of act one, expect most of Vice City visible. By the end of the game, the full map. The pace varies.
Probable starting areas
Speculative. Rockstar games usually start with the protagonists in a constrained context - GTA V started with a heist sequence in the snow. Trailer footage suggests Lucia and Jason's story may begin in or near a prison, then progress out into Vice City.
First playable region is almost certainly part of Vice City or its immediate surroundings. The wetlands and the Keys analogue are likely later-game reveals.
First-day priorities (editorial picks)
Drive the bridge route to the Keys once it's accessible. Take a helicopter or aerial route over Vice City to get a sense of layout. Visit the art deco strip at night. None of these are required - they're just the moments most worth experiencing first.
What to be patient about
The full map taking time to unlock. Server and login issues - GTA Online had a difficult launch. Some content (multiplayer, online modes) likely arriving after singleplayer rather than alongside.
Don't expect everything to work cleanly on day one. Rockstar launches are messy.