If I make a new photo library can I just import from iCloud ?

When you are syncing a new, empty Photos Library with Photos, you will get all media files (photos, videos) back, that have ben uploaded to iCloud Photos, with all metadata like keywords, titles, captions, plus all albums and folders, like Yer_man has already confirmed. There will be two things that will be missing, however:

• Your projects are not synced between your devices, so your slideshows will be missing and any print projects you may have created, like photo books, cards, calendars. If you have projects to save, you need to keep your old library.
• There may also be some named faces missing in People & Pets. I have frequently restored my iCloud Photos Library from iCloud, and not all named faces came back, particularly the faces I added manually by drawing circles around the faces. It has to tag all photos with named faces with keywords (the name of the person as a keyword), so we can search with smart albums for photos where the the name of the person is missing and add the names back.

It sounds like you want a bunch of the same stuff, but not all-- is that right? Is there any indication that your current Library has any corruption-- any pictures that don't copy to iCloud Photos, for instance?

If the Library is good, I think the I would duplicate it for safe keeping, and then delete stuff I didn't want. It's easier to delete than trying to transfer stuff you want to keep. Since you have a copy, then if you decide later you didn't want to delete that picture, you can find it in your copy. Deleting stuff will also delete the same stuff at iCloud.com-- but you have the safe copy.

Deleting an album doesn't delete the pictures in it. Deleting a folder deletes all the albums inside, but not the pictures.

Lots of albums isn't a problem if you put albums together in folders. And you can put folders into folders. So you can have folders for decades, with year folders inside, and date albums inside those. 100 years will be in 10 folders, and you can find stuff quickly.

You can also have a folder of Vacations, with one folder inside organized by place and another one folder inside organized by season, etc. A picture can be in many albums without taking up any more space, so you can have lots of ways for finding that one picture you were thinking about. You can duplicate an album, so the same album can be in different folders without taking any more storage space.

Lots of people here have been struggling with organization for quite a while, so there's lots of experience you can draw on!

If you make a new library and sync with iCloud you'll get the same as you have now. But you can import photos from an external of course.