Perhaps you like the Guests App. You do not need a password because the user defines the password. Because of security reason it makes no sense to send a url and a password to the same email-address (in one or two emails). That is stupid.
It also makes no sense to define a only-one-download. Afterwards the user can copy all million times.
If you need it search “burn after reading” e.g. https://privatebin.net
Also search Jirafeau and FileShelter
Would be a nice nextcloud app. Perhaps someone like to program it.
Perhaps you can write a cron process to delete all guest users at midnight 
Also you can delete manually the guest users or the shares to guests.