Mass delete old thumnails and restrict the number of new thumbnails?

Every time I upload a new image to my site (which is daily), it creates 7 different thumbnails, even though I only show three sizes in my media settings and I only really need a single thumbnail size for the featured image.

1. How can I restrict the number of thumbnails WordPress is creating so it doesn’t take up so much space on my server with images I don’t need?
2. Is there a plugin or easy way to go back and delete all old thumbnails so that when they’re rebuilt it only creates the sizes I actually need?

Thanks in advance!