If you need to set up separate projects with the same files, you can drag and drop multiple files or even folders into another project. This does not move the files but it copies them into the new project without taking more space in your account.
If you copying files between projects that span across different teams, this will duplicate the storage usage. Each Team is completely separate from each other. Once you copy the files from one team to another, it will count towards that team's storage, but if you copy the files within the same team, this will be recognized and linked to that media within that team.
This will not copy comments nor share comments and the separate clips have their own URL too. To copy comments from one clip to another, learn about the copy/paste options here. If you delete the file from the original project, it will still exist in the new project too.