Answers for "new user vs user.create mongodb"

mongo create user

db.createUser(
  { 
    user: "user_name", 
    pwd: "password", 
    roles: [
      "userAdminAnyDatabase", 
      "dbAdminAnyDatabase", 
      "readWriteAnyDatabase"
    ]
  }
)

mongodb create user

use admin
db.createUser(
   {
     user: "restricted",
     pwd: passwordPrompt(),      // Or  "<cleartext password>"
     roles: [ { role: "readWrite", db: "reporting" } ],
     authenticationRestrictions: [ {
        clientSource: ["192.0.2.0"],
        serverAddress: ["198.51.100.0"]
     } ]
   }
)