Yes. those are indeed the templates you will need to override.
You don’t need to create both a plugin and a theme component.
You can override both templates from within a theme component. A good example is the Discourse Topic Author theme component.
But you can only use a theme component for this if the desired information is already present in the json for the topic list. If it’s not, then you will need to use a plugin that does not only override the theme components but also serializes the information to the json.