Archetypes are optional and define the narrative role a character fills in the game. Each world of OSR+ introduces a handful of archetypes unique to that world to give the players clear examples of how their characters can fit into the general feel of the setting. In A Quest of Queens, these roles are especially clear, because the PCs create characters who are part of the Queen's retinue. Each archetype is designed to represent a role a PC might fill in that retinue: as Counselor, Executioner, Mirthmaker, Plague Doctor, Knight, Outlander, and Spider.
Designing Archetype Abilities
Archetype abilities are the most narrow and least powerful of all. They're usually very context-specific, and present either a specific passive or active ability.
Other Uses for Archetypes
Archetypes can also be used to fill the gaps. If you have a campaign setting where the players may only choose Humans for their PCs (as is the case in Ride the Lightning and God Beyond the Portal), you can use archetypes to confer the sort of abilities that would be expected from origins, such as broad advantage or disadvantage.