If you link a collection into a .blend file and just want to manipulate in space a row of solar panels without changing count or spacing of array, you do not necessary need to create a library override.
You may just add collection instances.
If you add a library override on a collection instance(object), you create a collection (group/layer), locally. That collection (group/layer) is visible in viewport but could be disable/hidden in viewlayer.
So, if you modify that collection, all collection instances relative to it will be modified.
So, if you want a variation, you need to do right click > Duplicate Linked in outliner to copy collection (layer/group).
Now, you have another collection (group/layer) that have its own overrides.
You may be dealing with lots of objects in outliner of final .blend file but this data is really linked from another one.
A modifier is per object. By using multi-object editing (alt key pressed while modifying a setting), you can change all modifiers on all selected objects at same time.
But if you want to deal only with one object and one modifier, you need to join all parts of a solar panel into a unique object in original .blend file.
Array modifier is not the only way to create an array of instances.
You can use Instancing panel of Object Properties or you can instance through particles.
With these methods, you can instance a simple linked object or collection instances.