If during your use of these models you happen to come across some sort of issue with a particular mesh then please message me so that I may go ahead and fix the problem as soon as possible.

No, the meshes do not have custom UV unwrapping.

The objects do not have materials nor any material slots assigned to them, so you can rest easy that when copying these greebles in your scene you won't also be copying weird materials alongside and won't make a mess of your clean material list.

Yes, you may use the greebles however you wish inside your Blender scenes, either through the add-on, or by manually importing your favorite greebles in a scene to use with a particle hair system or whatever else crosses your mind.

If you have some specific greebles in mind that you just can't find anywhere else then by all means please feel free to message me with some details about what you're looking for and I may create those greebles for a future update to this pack or a new pack.