Do not delete the photos from "Imports" , unless you want the photo gone everywhere.
Photos is showing you many albums, but each photo I only stored once, no matter in how many albums the photo appears. There is just one copy of the photo in your library. The albums are referencing the photos in the library and showing you different views of the same photos, but the albums are not storing the photos.
Dealing a photo from "Imports" will remove it everywhere.
The only exception are shared albums. When you add a photo to a shared album, you are creating a new, smaller copy of the photo for sharing.
if you want to see which photos from your recent import have not yet been added to an album, you can use a smart album. File > New Smart Album. Use the rule "Album > is not > Any". Combine it with "Match All" with the rule "Date added is in the last 30 days" to see only the most recently imported photos.