Can you create NPCs without mods / plugins in Minecraft?

I would like to create NPCs on my server without mods / plugins that have certain textures and functions - is that possible?

You won't get very far without plugins. As far as I know, you can't set the job of more than one villager and stop what he does.

Well with datapacks you can do a lot with any entities including inventory that opens and click event for certain items…