could anyone please shed some light if I delete any of the images in LR, does its associated 1:1 preview gets deleted as well? If not, what is the best way to clean up after a huge number of deletes.
There are two options when you 'delete' images from Lightroom.
You can 'remove' the image from the catalog ... which hides it from view within Lightroom but retains the original image file in place wherever you first saved it.
Or ... you can also delete the image from the Lr Library and delete it from your drive.
This choices are clearly presented in the dialog when you choose to delete.
Both options will remove the corresponding previews from Lightroom. No housekeeping necessary.