EDITING + WORKFLOW: If I delete my old presets, will I lose the previous editing?

No, when you select a preset, the settings are all stored either in the .XMP sidecar file or in the Lightroom Catalog. Deleting the presets will not change this.

However, if you switch computers or wipe your hard drive in the future, you’ll need to have the old camera profiles installed still or else the previous edits won’t look right as they still need to call upon those. To avoid this, run your original installer on your new machine so the the original profiles get installed and delete the presets that it puts in Lightroom/ACR to avoid any clutter.