Basically each library has a different view and a different list of songs.
For a while (been using this product for many years) I tinkered with multiple libraries. But in my collection (80 thousand tracks and growing) there is too much overlap of genres and desires to play certain songs in different contexts to keep them physically separate. And putting the same track into multiple libraries was doomed from the start, impossible to manage, as already stated.
Now, I use ONE library for everything that is music. (I have a separate library for talk recordings, ranging from comedy to radio shows). I mean, ALL music, ranging from jazz to rock, classical to pop, showtunes to blues. I worried about this at first but it works fine (thank to MC's ability to handle a very large database), and again, there's too much overlap to NOT do this.
For what you are doing with separate libraries, I do with MC's formula-controlled playlists known as smartlists.
I use a combination of a few standard and custom fields to tag every track. Then smartlists easy and reliably grab the appropriate songs for whatever purpose. With the right field contents up-front, I can later create new smartlists for purposes I haven't yet thought of. All I need to do is a good job of tagging in the first place. Just understand that some custom fields (tags) are necessary, especially multi-value fields since MC has many fields locked-down as single-value for compatibility. My most powerful tool is the standard Keywords field. (I could have created a similar custom field, but didn't find a need.) A given track might have two (usually the minimum) values in the Keywords 0field, but some have 10 values.
I could come up with many examples, but one that got played today (I love "random" playback) makes the point: In 1964 there was a hit record "I Want To Hold Your Hand" by Arthur Fiedler conducting the Boston Pops Orchestra. That one song is reasonably categorized as classical, pop, Beatles, rock, orchestral, 1964, instrumental, etc. and there are two artists, Arthur Fiedler and The Boston Pops Orchestra -- two because they both recorded separately, Fiedler with other orchestras and The Boston Pops with other conductors. A lot going on for just ONE song, but easily categorized via some standard and custom fields so I can include it (or not) in any playlist based on many criteria.
Different views for different playlists is easy. A playlist/smartlist always has its own view design -- just customize it. In fact, it's actually a bit of a pain to give several playlists the SAME view design (due to what I hope is a yet-to-be-finished aspect of MC13's save/load view design action).