Lightroom Classic Catalog using most of my hardrive space?

You do understand that your photos are not in the catalog, correct?

The catalog is a database (SQLITE) containing records of where your photos are, and what post processing edits you apply, both metadata, and develop.

In addition to the catalog, LrC creates several folders containing library module previews.

LrC can backup your catalog upon exit, that is an option (on by default) 

The backup just backups the catalog, not the photos. The backup does not backup the application, it dies not (normally) backup presets, profiles, etc.

You can control where the backup is or is not placed.

Backups should be located on separate hard drives, not the hard drive the original files are located on, and best practice is to have several, at least two, on different drives, external drives are popular for this.

You might want to look at:

https://helpx.adobe.com/lightroom-classic/kb/catalog-faq-lightroom.html

https://mastering-lightroom.com/lightroom-space-part-1/

https://mastering-lightroom.com/lightroom-space-part-2/

My photo files occupy 560 GB, my LRC catalog + previews folder is 41 GB, and my latest catalog backup zip is 671 MB. You can see that the catalog is significantly smaller then the collection of Raw files. I suggest you search for slow-down problems elsewhere.

You can disable this LR catalog only backup from that product in preferences. IMHO, it's not very useful as you need a full (all documents and files) backup schema and this isn't it. So no, you do not need a backup zipped catalog from LR, you DO need a full backup plan for all data. 

It's not clear from your description if you deleted the catalog, or the backup catalog. Lightroom Classic runs on a catalog. It requires the catalog. If it can't find a catalog when you open the application it will create one. You don't want to delete your working catalog.

Backups are simply a copy of the catalog with all the previews and metadata. It's okay to delete backups. I usually keep the most recent three. It's best to save backup catalogs on a different drive than the working catalog. This ensures you have a backup in the case of a drive failure. The back ups also won't fill up the start up drive.

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