Can I delete my account and all my photos permanently if I decide to leave?

Yes. At the album level, the edit page has a permanent delete for each album — download anything you need first, because there's no undo. At the account level, the "Request Data Deletion" flow handles full removal. Between those two, you can cleanly exit with your files in hand. The one thing to keep in mind is the order of operations: download your originals before you delete albums or request account removal, because after that there's no going back.