You don't really 'import' to the Organizer. Contrary to Bridge, which is a dedicated photo browser, the Organizer works like Lightroom. It can 'Import" = download files from 'removable media' (cards, CD, DVD) or from camera to your drives (external USB drives are considered just like internal drives, not removable ones) then it 'registers' and 'indexes' the location of each file (drive and path) into the catalog database. The catalog contains only links, like in Lightroom. If you browse the files in your catalog in the left 'folders' panel in tree mode (not list mode) you can see the folder tree like in the Explorer, including all connected drives, internal or external, removable or not.
If you 'upload' a raw file, it will be copied where you decide and be registered in the catalog. When you open it in the ACR converter plugin, after your edits you can either click 'Done', which saves your edit in an xmp sidecar file and in the catalog, or you can click 'open' to open it in the normal pixel editor where you can further edit, then display, print or save in any format including jpeg. Note that the 'Save' button does not save to jpeg, it only converts proprietary raw formats to DNG. So to get jpegs, you have to 'Open' in the editor first. Depending on your preferences, the jpeg version is linked to the raw files in a 'version set' and saved by default on the same location (not mandadory in Elements).
You can still use Bridge together with the ACR version of Elements, which is limited compared to the full Photoshop version or the LR features. However, beware that moving, renaming or deleting files outside of the Organizer will kill the links recorded in the catalog and make the files 'disconnected' or 'missing'. Such changes must be done from the organizer only.
About space on your drive:
There is no duplication of files in the catalogs.
Catalog folders don't take much space and you can locate and see them from the menu Help >> System information.
The catalogs are by default in a 'hidden' location on your master drive, but you can move them to an external drive if that matters, for instance storing the catalog together with the media on an external drive makes you able to share them between two computers just by plugin the external drive alternatively to share the same library.