Difficult to delete "some" in bulk! because they are stored in a folder with cryptic filenames. The .XMP files have within them the Preset Name and Group name that you see in the Lightroom interface.
1) Find out where your LR Catalog is stored. You can do this in Lightroom CC by going to “Adobe Lightroom CC > Preferences” in the menu..
2) then select “Local Storage” from the left-hand tab. And towards the bottom, it should list the storage location of your catalog. Click on [Browse].
3) You should see a ‘Data’ folder with a bunch of random letters and numbers, like “ab414778e2e444859150c9a15f1481da”. Go into that folder, then the “cr_settings” folder. All of your presets are in there.