5e is predominantly a game about intricate PC combat builds, and GM-driven adjudication of non-combat action. So the 1st adventure for One D&D should showcase this. Something similar to Dragonlance would therefore be a good fit: a quest which requires a group of unlikely comrades to join together to travel to strange places, where they have to fight to get the thing they're there to get. There should be some NPCs that allow players with social-oriented PCs to do their thing - but the progression of the adventure should be largely independent of how those NPCs end up responding to the PCs.