How do I define EOS Achievements for a DLC (separate from basegame)?

We released our game on EGS not long ago and an expansion DLC with more content is on the way. My question is: if I want to define more achievements specifically for the DLC, how can I do that?

Should I just add them to the list of achievements defined for the basegame? In this case, will they appear along the basegame achievements, essentially blocking players from reaching 100% without buying the DLC?

Is there a way to define them tied to the DLC, similarly how achievements on other platforms work, where your DLC achievements (as a player) are visible under a different achievement group?