2 copies in different collections

The pictures are not "stored" in collections, they are referenced by the collections.

The one file of the picture is "stored" in the folder on disk.

Since you want to make multiple edits to the same picture, virtual copies is the correct path to take.

However, I would recommend making that virtual copy in the folder from the Folders panel, then drag the VC to the collection. That way the other collections never see the VC.

OK, so just to clarify a couple of things you need to be aware of,

The image files that have been imported into Lightroom show in the left panel of the Library Module in the folder structure depending to where they are located in you hdd or network storage where they are located.

When you assign images to a collection they will show up in the left panel of the Library Module under the Collections header. You can assign image files to multiple collections as you are already aware.

Collections do not contain actual image files or copies of the original, it just information stored in the Catalog file.

Changes made from the any of the collections will be reflected in the original file and in all the collections where it has been assigned.

When you create a virtual copy of an original (and you can create multiple virtual copies) it is not an actual image file, hence It’s virtual and info stored in the Catalog File. The virtual copy will show alongside the original file in the Folder structure with the bottom left edge turned over.

The Folders and The Collections have a different appearance.

Create virtual copies, so then you can have multiple different appearances, the virtual copy with "cool changes with presets" in collection A and the virtual copy with black and white in collection B.