The best way to trigger game events in a list

I'm trying to create a system that can read through a list of "game events" and activate them accordingly, but am having difficulty creating a solid, efficient approach that's easy to expand and work with. A pseudo-code example of what I mean is

 manager.Text(player_portrait, "Hello!")
 manager.Move( npc, 2, -2)
 manager.ShowImage("random bottle")
 manager.Text(npc_portrait, "Do you like my bottle?")
 switch (manager.Choice(Yes, No))
 {
     case 1: {
         manager.Reward(Reward.Gold, 100);
     }
     case 2: {
         manager.StartBattle("crazy person");
     }
 }
 manager.Text(player_portrait, "That was odd.")
 }

My question is: what's the best way to achieve this?

I've tried having a base class "gameEvent" that all events (text, move, reward, battle, etc.) derived from, but Unity is not keen on polymorphism and I couldn't get a List where I could edit each member of the list inside the Unity Editor (I tried custom editors and property drawers, I had issues with Unity's serialization).

I'm currently toying with the idea of creating a Unity Script (C#/JavaScript, whatever) for every "event thread" as it were, which would just call lots of functions in a "manager" class, but I feel this would seriously bloat my project file, as it's an RPG and I imagine using this game event system for talking to all NPCs, controlling cutscenes, random or scripted battles, or the like.

I've thought about using XML - or even a binary file, created external to Unity - that could be read in, but I worry about the performance issues for that? First there's looking up the file and then I believe also that parsing strings is not very desirable for performance.

From reading around this site I feel I might be able to do this with delegates, but I can't see how I could customise the inputs (such as varying text) for each delegate in the list?

Anyway, I understand this question is kind of vague, but I'm just curious what other people would try? I've only been working with Unity for a little over a year and I know there's a lot more I can do with learning.

P.S. This is my first question on here, apologies if it's badly formatted! I've tried searching for existing answers, but am having difficulty coming to a conclusion.

EDIT: I had some formatting issues with my pseudo-code, so I fixed it to look a bit more like C#.