It depends on your account's privacy settings. If you're a public account, removing someone doesn't prevent them from seeing your profile, posts, or Stories. They can still view everything — and even send you messages. Your content just won't show up on their feed anymore. They can also refollow you at any time unless you block their account. On the other hand, if your profile is set to private, removing a follower will prevent them from seeing your content. They may request to refollow you, but you will have to approve them in order for them to see your posts and Stories again.