They mean different things. "Set someone off" usually means "get someone started" for example "winding them up" and making them angry, or helping them begin their journey. "Drop someone off" is much more common - it means you are driving them somewhere - "giving them a lift", like a taxi driver. Taking them to their destination. You can also drop off a package (deliver a package), like a courier.

Native speakers almost always say “drop someone off.” Example: I’ll drop you off at the station. “Set someone down” is correct, but it sounds old-fashioned or very formal. You might see it in books, not in everyday speech. Literally, “set someone down” means to put someone on the ground after carrying them. Example: He set the child down on the floor. Other natural alternatives are: Give someone a ride to… Take someone to… So the most common and natural phrase is “drop someone off.”

Hi Alina We wouldn't really set someone down. Although, we can set someone off by making them excited or angry about something. We use drop of when we take and leave a person at a particular destination. For example: I drop my kids off at school in the mornings. I asked the taxi driver to drop me off at the bust stop. I hope that makes sense and clears things up a bit for you :)

"Set down" is entirely different from "drop off": "She set the baby down in its high chair" "The pilot set the plane down smoothly on the runway" "The teacher set down clear rules against cheating" The verb "set" conveys intentional action, whereas "drop" is vaguer and can be unintentional: "He dropped his keys somewhere on the sandy beach. They will never be found." Consider "She dropped her daughter off at school". Although the action is intentional, "drop" works better than "set" because she did not pick her daughter off and carefully put her down. "Set" would sound too specific, but it wouldn't actually be incorrect.