Really stupid TS3 question about the recent upgrade with "active packs" *update, not upgrade-- only through my first cup of coffee this am

Now when it says it may affect my saves if I have different packs active while playing... if I uncheck the boxes for, say, Late Night, will all the content included in Late Night not show up? Or does it just mean I'm not playing that specific pack? Why would I buy all this shit if I didn't want to play it all at once? My game takes a century to load, otherwise I would just open it and try, I didn't want to mess everything up by loading up with a single pack to find everything screwed up because of missing content.