You might just want to add the custom target selector option also, but I'm still not quite sure how useful that is.
Speak to Individual Players
This means that whoever clicks on the NPC and acquires the @s so to speak, is the one who sees the tellraw, and nobody else
Note that if timing is still handled externally by 1 entity, more than 2 players cannot initiate delays at the same time
Consider fixing this somehow: We will probably shift the burden on timer variables to the player that initiates. Your initiator scoreboard allocation idea might be the way to go with this one.
Speak to All Players
This means that regardless of who clicks on the NPC, all players will see the tellraw that is spoken
Use case for custom selector input by user: you want NPC dialogue to be heard by (all) those nearby, but not everyone in the world
If we end up implementing this, we should probably give the player an option to add custom target selectors
You might just want to add the custom target selector option also, but I'm still not quite sure how useful that is.
Speak to Individual Players
@sso to speak, is the one who sees the tellraw, and nobody elseSpeak to All Players