I have done a stupid mistake that has erased my Downloads folder. I'd like to restore them with the proper permissions and metadata. Can somebody tell me what they are by default for a regular user and in /Users/Shared?

You can simply post the output of those commands:

ls -l@d /Users/"$USER"/Downloads | sed "s/$USER/the-username/g"
mdls /Users/"$USER"/Downloads | sed "s/$USER/the-username/g"
ls -l@d /Users/Shared/Downloads
mdls /Users/Shared/Downloads