Deleting posts with their featured images

This is a very basic question, so basic that I had a very hard time finding a Googled answer since the answer is so taken for granted nobody bothered to talk about it.

I have used in the past months a premium plugin that imports blog/article feeds into posts residing on my server. The images within the articles are not imported but remotely referenced through “href”. Only the featured image is imported.

Thousands of posts have taken up a lot of space (mostly from the featured images) and I need to delete many of the posts and their associated featured images, some manually using wp-admin and others in bulk using a bulk delete plugin.

1. Does deleting posts also delete the featured image too? (hopefully)
2. Is it a factor whether the featured image was added by the feed import plugin or added using the media button?

Any clues from WordPressers would be greatly appreciated.