Just a couple of corrections on that link @ZeeGee provided for organising - Worlds CAN be installed without the launcher, if the creator provides a .world file. These are put into the EA game install directory on C drive, in Sims 3\GameData\Shared\NonPackaged\Worlds
I have never extracted a world with PackageExtractor, so I can't speak for that, but I have playtested worlds, after being given a .world file to put into the directory listed above. You simply choose the world from the drop down menu in game as normal.
Secondly, to avoid any confusion when wanting to extract a package from a sims 3 pack, I find it more helpful to open the s3pack with Custard, untick the unwanted CC items, leaving only the single file I want, save the pack and then extract it with Packager Extractor. It's an extra step, but it saves you having to fiddle about in s3pe trying to identify which package was extracted from the pack.
Also, when extracting sims, I always simply rename the extension on the file from .package to .sim and drop it into my saved sims folder. In my previous experience, keeping extracted sims as a package and in the mods folder never worked as they never showed up in CAS. Perhaps something has changed, I don't know.
If the "sim" in question is in a household and you want to extract them, then leave them as package and drop them into the Library folder.
I never download patterns made with EA's pattern maker, and I never download lots or sims with CC either. I clean out every lot of sim I download first, even if I have the CC items included. That way, I can be absolutely certain that no CC I haven't chosen gets into my game. S3 can be very temperamental, and my game is at a stage when it runs beautifully, despite having a couple of gigs of CC, and is giving me no problems, so I like to keep it that way :)
S3PECustardSims 3 Pack Multi Extractor