Maximum NPCs in a mobile game

As far as I know there are no documented guidelines for maximum number of NPCs in a mobile world, but some things to keep in mind would be that NPCs basically use the same resources as player avatars and each world is capped at 32 player avatars. The same is true for any other gizmo, you can use as many as you want as long as your world stays above 60 FPS. It is always a balance between adding too much and keeping a performant world.

You can spawn NPCs, but I don't think you can spawn them with a random name, and certainly cannot spawn them with a random look right now. Alternatively you could setup a collection of NPCs, save them as an asset then spawn that asset.