With combat I create interesting terrain, interesting enemy mechanics, cool boss fights, etc. First bucket is one you mentioned. Incidental interactions.
The players step up and chat with an NPC. You want some great gameplay in these encounters like you get from your interesting combats. And things get boring fast. Another approach: the NPC resists giving the party goal achievement because the cost to them is high. Cost of failure in combat is easy to assess. In our example, the bartender could suffer punishment if the mafia finds out he gave up their clubhouse.
So the bartender must make a calculation. How much money is worth the risk? Can he explain himself to the mob if revealed and live? The cool thing thing is we can use the same combat design skills to create interesting roleplay encounters.
You could make this location the stands at an arena match, in a dark alley in a dangerous part of town, in a sauna, the forest during a hunting trip. Physical aspects do not matter as much as in combat encounters. But design with Cost and Stakes in such a way that you make the encounter harder or easier.
How about the bartender brings along their trusted best friend as bodyguard to meet in an abandoned building on the poor side of town at 4 a. The bodyguard gives the bartender extra confidence and good advice, making certain roleplay approaches more difficult, such as bullying.
