Then, can I copy some or all of the contents from one to another and still have them be separate entities?

Anything you copy is simply a link to the original thing. Actually, the original thing is just a link, too, everything is a link in Emplode.

For instance. If you copy a playlist, it's just a link to the original playlist. So if, for example, your "alternative" playlist has a bunch of sub-playlists such as "Pearl Jam", "Stone Temple Pilots", etc., then if you copy those playlists to your other "alternative" playlist, then any changes you make to the first "Pearl Jam" playlist will be reflected in the other one, too. For example, if you get a new Pearl Jam album and you add it to one of those playlists, then that new album will appear in the other playlist, too.

If you want two completely different "Pearl Jam" playlists with different contents, then don't copy it, create a new one from scratch.

Same thing with songs. Each song index is just a link to the actual song file. So if you have two completely different "Pearl Jam" playlists (each created separately), and you copy "Jeremy" from one of the playlists to the other one, then if you edit the tag data (title, artist, year, etc.) in one of the copies of "Jeremy", then the other one will reflect those changes, too.

Everything in Emplode is just a link to a database entry. So when you make a copy in emplode, you're just making a new link in a new place. Any edits are to the underlying database entry.

If you want something separate, create it using the "new" option instead of copying it.

This sounds more confusing than it actually is. In practice, it's actually very convenient. For example, you could create a "Jazz" playlist with a sub-playlist of "Pat Metheny". You could also have a copy of the "Pat Metheny" playlist in your "Artists MNO" playlist. When you got a new Pat Metheny album, you add it to one and it automatically appears in the other. See?